perf machine: Fix mmap name setup

perf machine: Fix mmap name setup

Leo reported broken -k option behavior. The reason is that we used
symbol_conf.vmlinux_name as a source for mmap event name, but in fact
it's a vmlinux path.

Moving the symbol_conf.vmlinux_name check for both host and guest to the
proper place and out of the machine__set_mmap_name function.

Reported-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Leo Yan <leo.yan@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: commit ("8c7f1bb37b29 perf machine: Move kernel mmap name into struct machine")
Link: http://lkml.kernel.org/r/20180312152406.10141-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>