perf pmu: Fix usage of __ in struct names

In tools/perf we use a convention where __ separates the struct name
from the function name for functions that operate on a struct instance.

Fix this usage by removing it from the struct names and fix also the
associated functions.

Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-1tepcpohpvfg589pizx7tlkq@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>