perf symbols: Move mem_info and branch_info out of symbol.h

The mem_info struct goes to mem-events.h and branch_info goes to
branch.h, where they belong, this way we can remove several headers from
symbols.h and trim the include dependency tree more.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-aupw71xnravcsu2xoabfmhpc@git.kernel.org


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