perf intel-pt: Rationalize intel_pt_sync_switch()'s use of next_tid

Returning 1 from intel_pt_sync_switch() causes the current tid to be
set. That negates the need to keep next_tid anymore. Rationalize the
code to that effect.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190412113830.4126-9-adrian.hunter@intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>