Currently we pass this for u-boot-spl.kwb targets, however when
building sunxi-spl.bin in the TOC0 format we may also need to
specify a KEYDIR, as such we should also pass this when set
to mkimage for the sunxi-spl.bin target.
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>