perf tools: Rename and move pmu_event_name to get_config_name

perf tools: Rename and move pmu_event_name to get_config_name

Following commits will make more events obey /name=newname/ options.
This patch makes pmu_event_name() a generic helper.

Makes new get_config_name() accept NULL input to make life easier.

Signed-off-by: Wang Nan <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Brendan Gregg <[email protected]>
Cc: Cody P Schafer <[email protected]>
Cc: He Kuang <[email protected]>
Cc: Jeremie Galarneau <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kirill Smelkov <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Zefan Li <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>