drm/radeon: make VM flushs a ring operation

Move flushing the VMs as function into the rings.
First step to make VM operations async.

Signed-off-by: Christian König <deathsimple@vodafone.de>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>

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

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

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

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

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

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

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

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