dma-resv: Fix kerneldoc

Oversight from

commit 6edbd6ab
Author: Christian König <christian.koenig@amd.com>
Date:   Mon May 10 16:14:09 2021 +0200

    dma-buf: rename and cleanup dma_resv_get_excl v3

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Link: https://patchwork.freedesktop.org/patch/msgid/20210622165511.3169559-2-daniel.vetter@ffwll.ch