drm/radeon: unlock the ring mutex while waiting for the next fence

Fixing just another deadlock problem with gpu reset tests.

Signed-off-by: Christian König <deathsimple@vodafone.de>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
1 file changed