uboot-imx

MIPS: handle mips64 ST0_KX bit in mips32 start.S

In preparation for sharing a single copy of start.S between mips32 &
mips64, handle setting the KX bit of the cop0 Status register when the
mips32 start.S is built for mips64.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>