misc: fastrpc: Fix return value check in fastrpc_map_create()

In case of error, the function dma_buf_get() returns ERR_PTR() and never
returns NULL. The NULL test in the return value check should be replaced
with IS_ERR().
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/fastrpc.c

@@ -496,8 +496,8 @@ static int fastrpc_map_create(struct fastrpc_user *fl, int fd,
 	map->fl = fl;
 	map->fd = fd;
 	map->buf = dma_buf_get(fd);
-	if (!map->buf) {
-		err = -EINVAL;
+	if (IS_ERR(map->buf)) {
+		err = PTR_ERR(map->buf);
 		goto get_err;
 	}