drm/amdgpu: use DMA_RESV_USAGE_KERNEL

Wait only for kernel fences before kmap or UVD direct submission.

This also makes sure that we always wait in amdgpu_bo_kmap() even when
returning a cached pointer.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220407085946.744568-6-christian.koenig@amd.com