perf machine: Ditch find_kernel_function variants

Since we do not have split symtabs anymore, no need to have explicit
find_kernel_function variants, use the find_kernel_symbol ones.

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-hiw2ryflju000f6wl62128it@git.kernel.org


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