perf trace: Move vfs_getname storage to per thread area

perf trace: Move vfs_getname storage to per thread area

We were storing the vfs_getname payload (i.e. ptr->string) into
the trace wide storage area (struct trace), so that we could use the
last payload when setting up the fd->pathname per thread tables, oops,
not a good idea for multi cpu tracing sessions...

Fix it by moving it to the per thread area (struct thread_trace).

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-3j05ttqyaem7kh7oubvr1keo@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>