RDMA: use dma_resv_wait() instead of extracting the fence

Use dma_resv_wait() instead of extracting the exclusive fence and
waiting on it manually.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Maor Gottlieb <maorg@nvidia.com>
Cc: Gal Pressman <galpress@amazon.com>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20220321135856.1331-4-christian.koenig@amd.com