dma-buf: fix stale @lock references in struct dma_buf documentation

The kernel-doc comments for vmapping_counter and vmap_ptr in struct
dma_buf reference "@lock" as the protecting lock, but struct dma_buf
no longer has a "lock" member. The mutex was removed in favor of using
the dma_resv lock exclusively. The implementation correctly uses
dma_resv_assert_held(dmabuf->resv) in dma_buf_vmap() and
dma_buf_vunmap(), so update the documentation to reference @resv
instead.

Signed-off-by: gaoxiang17 <gaoxiang17@xiaomi.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20260415054101.535520-1-gxxa03070307@gmail.com

Author: Xiang Gao

include/linux/dma-buf.h

@@ -322,13 +322,13 @@ struct dma_buf {
 	 * @vmapping_counter:
 	 *
 	 * Used internally to refcnt the vmaps returned by dma_buf_vmap().
-	 * Protected by @lock.
+	 * Protected by @resv.
 	 */
 	unsigned vmapping_counter;
 
 	/**
 	 * @vmap_ptr:
-	 * The current vmap ptr if @vmapping_counter > 0. Protected by @lock.
+	 * The current vmap ptr if @vmapping_counter > 0. Protected by @resv.
 	 */
 	struct iosys_map vmap_ptr;