mboot64: Fix atomics.

Atomic ops from the Linaro kernel.

Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>
mboot64: Update bitops for aarch64.

From linaro kernel, again.

Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>
mboot64: Update aarch64 byteorder.h

Again, Linaro kernel.

Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>
mboo64: Cleanup aarch64 headers.

Finish up sanitizing headers.

Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>
mboot64: Conditionalize some more drivers/modules.

I neither want xyzmodem nor PCMCIA support built in.

Signed-off-by: Andrei Warkentin <andrey.warkentin@gmail.com>