perf intel-pt: Move branch filter logic

intel_pt_synth_branch_sample() skips synthesizing if the branch does not
match the branch filter.  That logic was sitting in the middle of the
function but is more efficiently placed at the start of the function, so
move it.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1443186956-18718-14-git-send-email-adrian.hunter@intel.com


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