perf trace: Really free the evsel->priv area

In the Linux kernel, the following vulnerability has been resolved:

perf trace: Really free the evsel->priv area

In 3cb4d5e00e037c70 ("perf trace: Free syscall tp fields in
evsel->priv") it only was freeing if strcmp(evsel->tp_format->system,
"syscalls") returned zero, while the corresponding initialization of
evsel->priv was being performed if it was _not_ zero, i.e. if the tp
system wasn't 'syscalls'.

Just stop looking for that and free it if evsel->priv was set, which
should be equivalent.

Also use the pre-existing evsel_trace__delete() function.

This resolves these leaks, detected with:

$ make EXTRA_CFLAGS="-fsanitize=address" BUILD_BPF_SKEL=1 CORESIGHT=1 O=/tmp/build/perf-tools-next -C tools/perf install-bin

=================================================================
==481565==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 40 byte(s) in 1 object(s) allocated from:
#0 0x7f7343cba097 in calloc (/lib64/libasan.so.8+0xba097)
#1 0x987966 in zalloc (/home/acme/bin/perf+0x987966)
#2 0x52f9b9 in evsel_trace__new /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:307
#3 0x52f9b9 in evsel__syscall_tp /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:333
#4 0x52f9b9 in evsel__init_raw_syscall_tp /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:458
#5 0x52f9b9 in perf_evsel__raw_syscall_newtp /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:480
#6 0x540e8b in trace__add_syscall_newtp /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:3212
#7 0x540e8b in trace__run /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:3891
#8 0x540e8b in cmd_trace /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:5156
#9 0x5ef262 in run_builtin /home/acme/git/perf-tools-next/tools/perf/perf.c:323
#10 0x4196da in handle_internal_command /home/acme/git/perf-tools-next/tools/perf/perf.c:377
#11 0x4196da in run_argv /home/acme/git/perf-tools-next/tools/perf/perf.c:421
#12 0x4196da in main /home/acme/git/perf-tools-next/tools/perf/perf.c:537
#13 0x7f7342c4a50f in __libc_start_call_main (/lib64/libc.so.6+0x2750f)

Direct leak of 40 byte(s) in 1 object(s) allocated from:
#0 0x7f7343cba097 in calloc (/lib64/libasan.so.8+0xba097)
#1 0x987966 in zalloc (/home/acme/bin/perf+0x987966)
#2 0x52f9b9 in evsel_trace__new /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:307
#3 0x52f9b9 in evsel__syscall_tp /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:333
#4 0x52f9b9 in evsel__init_raw_syscall_tp /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:458
#5 0x52f9b9 in perf_evsel__raw_syscall_newtp /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:480
#6 0x540dd1 in trace__add_syscall_newtp /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:3205
#7 0x540dd1 in trace__run /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:3891
#8 0x540dd1 in cmd_trace /home/acme/git/perf-tools-next/tools/perf/builtin-trace.c:5156
#9 0x5ef262 in run_builtin /home/acme/git/perf-tools-next/tools/perf/perf.c:323
#10 0x4196da in handle_internal_command /home/acme/git/perf-tools-next/tools/perf/perf.c:377
#11 0x4196da in run_argv /home/acme/git/perf-tools-next/tools/perf/perf.c:421
#12 0x4196da in main /home/acme/git/perf-tools-next/tools/perf/perf.c:537
#13 0x7f7342c4a50f in __libc_start_call_main (/lib64/libc.so.6+0x2750f)

SUMMARY: AddressSanitizer: 80 byte(s) leaked in 2 allocation(s).
[root@quaco ~]#

With this we plug all leaks with "perf trace sleep 1".