kirkwood: fix Ctera C200 V1 ubi part name

In 749237967a downstream dts was replaced with upstream accepted
patch. But in upstream version last partition was called "rootfs"
instead "ubi". OpenWrt require "ubi" label for ubi rootfs.
This patch restore proper label.

Fixes: 749237967a ("kirkwood: Replace dtses with upstream accepted")

Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
(cherry picked from commit 9075cfd609)

target/linux/kirkwood/patches-5.15/114-ctera-c-200-v1.patch

@@ -49,3 +49,12 @@
  			function = LED_FUNCTION_STATUS;
  			color = <LED_COLOR_ID_GREEN>;
  			gpios = <&gpio1 7 GPIO_ACTIVE_LOW>;
+@@ -240,7 +252,7 @@
+ 	};
+ 
+ 	partition@7a00000 {
+-		label = "rootfs";
++		label = "ubi";
+ 		reg = <0x7a00000 0x8600000>;
+ 	};
+ };