drm/radeon: improve ring lockup detection code v2

Use atomics and jiffies_64, so that we don't need to have the
ring mutex locked any more and avoid wrap arounds.

v2: fix some checkpatch warnings

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

diff --cc drivers/gpu/drm/radeon/radeon.h
Simple merge

diff --cc drivers/gpu/drm/radeon/radeon_ring.c
Simple merge