images: bump default rootfs size to 256 MB

Signed-off-by: Felix Fietkau <[email protected]>

config/Config-images.in

@@ -260,7 +260,7 @@ menu "Target Images"
 	config TARGET_ROOTFS_PARTSIZE
 		int "Root filesystem partition size (in MB)"
 		depends on GRUB_IMAGES || TARGET_ROOTFS_EXT4FS || TARGET_rb532 || TARGET_mvebu
-		default 48
+		default 256
 		help
 		  Select the root filesystem partition size.