Define KERNELNAME to Image to get the build system to copy this image
over $(KDIR) automatically for us.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39768 3c298f89-4303-0410-b956-a3cf2f4a3e73