perf symbols: Remove map_type arg from dso__find_symbol()

perf symbols: Remove map_type arg from dso__find_symbol()

One more step to ditch MAP__{VARIABLE,FUNCTION}

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-919d1k13ts62pjipnpibvgwd@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>