media: rockchip: rkisp1: use device name for debugfs subdir name

While testing Rockchip RK3399 with both ISPs enabled, a dmesg error
was observed:
```
[   15.559141] debugfs: Directory 'rkisp1' with parent '/' already present!
```

Fix it by using the device name for the debugfs subdirectory name
instead of the driver name, thus preventing name collision.

Link: https://lore.kernel.org/linux-media/20211010175457.438627-1-mike.rudenko@gmail.comSigned-off-by: Mikhail Rudenko <mike.rudenko@gmail.com>
Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c

@@ -462,7 +462,7 @@ static void rkisp1_debug_init(struct rkisp1_device *rkisp1)
 {
 	struct rkisp1_debug *debug = &rkisp1->debug;
 
-	debug->debugfs_dir = debugfs_create_dir(RKISP1_DRIVER_NAME, NULL);
+	debug->debugfs_dir = debugfs_create_dir(dev_name(rkisp1->dev), NULL);
 	debugfs_create_ulong("data_loss", 0444, debug->debugfs_dir,
 			     &debug->data_loss);
 	debugfs_create_ulong("outform_size_err", 0444,  debug->debugfs_dir,