ramips: combine USW-Flex dual firmware-partitions

In order to maximize the available space on USW-Flex boards using a
dual-image partition layout, combine the two OS partitions into a single
partition.

This allows users to access more usable space for additional packages.

Don't limit the usable image size to the size of a single OS partition.
The initial installation has to be done with an older version of OpenWrt
in case the generated image exceeds the space of a single kernel
partition in the future.

Signed-off-by: David Bauer <[email protected]>

target/linux/ramips/dts/mt7621_ubnt_usw-flex.dts

@@ -164,14 +164,10 @@
 			};
 
 			partition@1a0000 {
+				/* Combine kernel0 / kernel1 */
 				compatible = "denx,fit";
 				label = "firmware";
-				reg = <0x1a0000 0x730000>;
-			};
-
-			partition@8d0000 {
-				label = "kernel1";
-				reg = <0x8d0000 0x730000>;
+				reg = <0x1a0000 0xe60000>;
 			};
 		};
 	};

target/linux/ramips/image/mt7621.mk

@@ -2130,7 +2130,7 @@ define Device/ubnt_usw-flex
   DEVICE_DTS_CONFIG := config@1
   DEVICE_DTS_LOADADDR := 0x87000000
   KERNEL := kernel-bin | lzma | fit lzma $$(KDIR)/image-$$(firstword $$(DEVICE_DTS)).dtb
-  IMAGE_SIZE := 7360k
+  IMAGE_SIZE := 14720k
 endef
 TARGET_DEVICES += ubnt_usw-flex