perf help: Do not use ALLOC_GROW in add_cmd_list

Replace ALLOC_GROW with normal realloc code in add_cmd_list() so that it
can handle errors directly.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20160510054752.6158.30562.stgit@devbox


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