perf evsel: Adopt find_process()

And make it static, nobody else uses it, if we ever need it in more
places we can carve a new source file for process related methods,
for now lets reduce util.{c,h} a tad more.

Link: http://lkml.kernel.org/n/tip-zgb28rllvypjibw52aaz9p15@git.kernel.org


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