amdkfd: Set *buffer_ptr to NULL in case of error

In function acquire_packet_buffer() we may return -ENOMEM. In that case, we
should set the *buffer_ptr to NULL, so that calling functions which check the
*buffer_ptr value as a criteria for success, will know that
acquire_packet_buffer() failed.
Reviewed-by: NAlexey Skidanov <alexey.skidanov@amd.com>
Signed-off-by: NOded Gabbay <oded.gabbay@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c

@@ -221,8 +221,14 @@ static int acquire_packet_buffer(struct kernel_queue *kq,
 							queue_size_dwords;
 
 	if (packet_size_in_dwords >= queue_size_dwords ||
-			packet_size_in_dwords >= available_size)
+			packet_size_in_dwords >= available_size) {
+		/*
+		 * make sure calling functions know
+		 * acquire_packet_buffer() failed
+		 */
+		*buffer_ptr = NULL;
 		return -ENOMEM;
+	}
 
 	if (wptr + packet_size_in_dwords >= queue_size_dwords) {
 		while (wptr > 0) {