ar71xx: allow to override kernel size in the CameoHornet profile

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@37833 3c298f89-4303-0410-b956-a3cf2f4a3e73
ar71xx: build factory image for DIR-505 A1

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt@37834 3c298f89-4303-0410-b956-a3cf2f4a3e73