perf tools: Refactor out kernel symbol argument sanity checking

User supplied values for vmlinux and kallsyms are checked before
continuing. Refactor this into a function so that it can be used
elsewhere.

Reviewed-by: Denis Nikitin <denik@chromium.org>
Signed-off-by: James Clark <james.clark@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20211018134844.2627174-2-james.clark@arm.com


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