rampis: mt7621: Edgerouter-X adjust IMAGE_SIZE to reflect new kernel size
IMAGE_SIZE was previously set to kernel1 + ubi size = 256768k, now
kernel1 is 6MB adjust this value to add 3072k to total image size.
Signed-off-by: Tim Lunn <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/15194
(cherry picked from commit 5b406bccaccadb494cad139b3f69e17ab62d3968)
Link: https://github.com/openwrt/openwrt/pull/17097
Signed-off-by: Petr Štetiar <[email protected]>