uboot-phytec

Makefile: Add size check to the u-boot.itb make target

The make macro to check if the binary exceeds the board size limit is not
called. Make sure that is the case.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>