drm/radeon: cleanup properly if mmio mapping fails

If we fail to map the mmio BAR, skip driver tear down
that requires mmio.

Should fix:
https://bugzilla.kernel.org/show_bug.cgi?id=56541

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
1 file changed