lantiq: set maximum kernel size for P2812HNUF3
The board has a fixed size kernel partition but do not limit the kernel
size during image building.
Disable image building for both boards as well, since the kernel of the
last release as well as master are to big to fit into the 2 MByte kernel
partition.
Signed-off-by: Mathias Kresin <[email protected]>
Mathias Kresin