drm/radeon/kms: Fix NULL ptr dereference

radeon_atombios_fini might be call while there is not valid
atombios structure allocated, thus test for a not null ptr
before trying to access this structure.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@linux.ie>
1 file changed