rampis: mt7621: Re-enable Edgerouter-X image builds

With the new layout providing 6MB for kernel there will be no issues
with kernel size affecting build of images.

Re-enable image builds for Edgerouter-X and X-SFP.

Signed-off-by: Tim Lunn <[email protected]>
Tested-by: Mauri Sandberg <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/15194
Signed-off-by: Petr Štetiar <[email protected]>

target/linux/ramips/image/mt7621.mk

@@ -2869,7 +2869,6 @@ define Device/ubnt_edgerouter_common
   DEVICE_COMPAT_MESSAGE :=  Partition table has been changed due to kernel size restrictions. \
     Refer to the wiki page for instructions to migrate to the new layout: \
     https://openwrt.org/toh/ubiquiti/edgerouter_x_er-x_ka
-  DEFAULT := n
 endef
 
 define Device/ubnt_edgerouter-x