perf map: Remove enum_type arg to map_groups__first()

perf map: Remove enum_type arg to map_groups__first()

Only the symbol core needs to use that, so provide a __ variant for that
case, that will end up removed when we ditch the MAP__ split.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-x29k9e1ohastsoqbilp3mguh@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>