drm/amdgpu: optimize insert_nop using multi dwords
Optimize the ring_insert_nop fn for n dwords in one
step rather then call to amdgpu_ring_write for each
nop packet. This avoid function call for each nop
packet and also wptr is updated once only.
Signed-off-by: Sunil Khatri <sunil.khatri@amd.com> Suggested-by: Christian König <christian.koenig@amd.com> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>