RDMA: use DMA_RESV_USAGE_KERNEL

We only need to wait for kernel submissions here.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220407085946.744568-9-christian.koenig@amd.com