RAS: Fix return value from show_trace()

Documentation/filesystems/seq_file.rst describes the possible return
values from a "show()" function used by single_open().

show_trace() returns the value of "trace_count". This could be
interpreted as "SEQ_SKIP", or just confuse the calling function.

Change to just return "0" to avoid confusing anyone reading this code
and possibly using as a template. Reading "daemon_active" was never
an intended use case.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221018165900.109029-1-tony.luck@intel.com