rv: Use strings in da monitors tracepoints

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

rv: Use strings in da monitors tracepoints

Using DA monitors tracepoints with KASAN enabled triggers the following
warning:

BUG: KASAN: global-out-of-bounds in do_trace_event_raw_event_event_da_monitor+0xd6/0x1a0
Read of size 32 at addr ffffffffaada8980 by task ...
Call Trace:
<TASK>
[...]
do_trace_event_raw_event_event_da_monitor+0xd6/0x1a0
? __pfx_do_trace_event_raw_event_event_da_monitor+0x10/0x10
? trace_event_sncid+0x83/0x200
trace_event_sncid+0x163/0x200
[...]
The buggy address belongs to the variable:
automaton_snep+0x4e0/0x5e0

This is caused by the tracepoints reading 32 bytes __array instead of
__string from the automata definition. Such strings are literals and
reading 32 bytes ends up in out of bound memory accesses (e.g. the next
automaton's data in this case).
The error is harmless as, while printing the string, we stop at the null
terminator, but it should still be fixed.

Use the __string facilities while defining the tracepoints to avoid
reading out of bound memory.