coresight: tmc-etf: Fix global-out-of-bounds in tmc_update_etf_buffer()

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

coresight: tmc-etf: Fix global-out-of-bounds in tmc_update_etf_buffer()

commit 6f755e85c332 ("coresight: Add helper for inserting synchronization
packets") removed trailing '\0' from barrier_pkt array and updated the
call sites like etb_update_buffer() to have proper checks for barrier_pkt
size before read but missed updating tmc_update_etf_buffer() which still
reads barrier_pkt past the array size resulting in KASAN out-of-bounds
bug. Fix this by adding a check for barrier_pkt size before accessing
like it is done in etb_update_buffer().

BUG: KASAN: global-out-of-bounds in tmc_update_etf_buffer+0x4b8/0x698
Read of size 4 at addr ffffffd05b7d1030 by task perf/2629

Call trace:
dump_backtrace+0x0/0x27c
show_stack+0x20/0x2c
dump_stack+0x11c/0x188
print_address_description+0x3c/0x4a4
__kasan_report+0x140/0x164
kasan_report+0x10/0x18
__asan_report_load4_noabort+0x1c/0x24
tmc_update_etf_buffer+0x4b8/0x698
etm_event_stop+0x248/0x2d8
etm_event_del+0x20/0x2c
event_sched_out+0x214/0x6f0
group_sched_out+0xd0/0x270
ctx_sched_out+0x2ec/0x518
__perf_event_task_sched_out+0x4fc/0xe6c
__schedule+0x1094/0x16a0
preempt_schedule_irq+0x88/0x170
arm64_preempt_schedule_irq+0xf0/0x18c
el1_irq+0xe8/0x180
perf_event_exec+0x4d8/0x56c
setup_new_exec+0x204/0x400
load_elf_binary+0x72c/0x18c0
search_binary_handler+0x13c/0x420
load_script+0x500/0x6c4
search_binary_handler+0x13c/0x420
exec_binprm+0x118/0x654
__do_execve_file+0x77c/0xba4
__arm64_compat_sys_execve+0x98/0xac
el0_svc_common+0x1f8/0x5e0
el0_svc_compat_handler+0x84/0xb0
el0_svc_compat+0x10/0x50

The buggy address belongs to the variable:
barrier_pkt+0x10/0x40

Memory state around the buggy address:
ffffffd05b7d0f00: fa fa fa fa 04 fa fa fa fa fa fa fa 00 00 00 00
ffffffd05b7d0f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffd05b7d1000: 00 00 00 00 00 00 fa fa fa fa fa fa 00 00 00 03
^
ffffffd05b7d1080: fa fa fa fa 00 02 fa fa fa fa fa fa 03 fa fa fa
ffffffd05b7d1100: fa fa fa fa 00 00 00 00 05 fa fa fa fa fa fa fa
==================================================================