drm/radeon: Update IH_RB_RPTR register after each processed interrupt

This might decrease the chance of IH ring buffer overflows.

Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

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

diff --cc drivers/gpu/drm/radeon/r600.c
Simple merge

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