perf symbols: Kill dso__build_id_is_kmod()

perf symbols: Kill dso__build_id_is_kmod()

The commit e7ee40475760 ("perf symbols: Fix symbols searching for module
in buildid-cache") added the function to check kernel modules reside in
the build-id cache.  This was because there's no way to identify a DSO
which is actually a kernel module.  So it searched linkname of the file
and find ".ko" suffix.

But this does not work for compressed kernel modules and now such DSOs
hCcave correct symtab_type now.  So no need to check it anymore.  This
patch essentially reverts the commit.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/20170608073109.30699-10-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>