perf machine: No need to check if kernel module maps pre-exist

perf machine: No need to check if kernel module maps pre-exist

We'only populating maps for kernel modules either from perf.data file
PERF_RECORD_MMAP records or when parsing /proc/modules, so there is no
need to first look if we already have those module maps in the list,
that would mean the kernel has duplicate entries.

So ditch one use of looking up maps by name.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-gnzjg2hhuz6jnrw91m35059y@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>