powerpc/mpc86xx: Disable translation for BAT setup

We really shouldn't be overwriting bat registers with translation enabled,
especially when we're executing code using one of them for translating
the current instruction stream.  Instead, disable address translation
while doing the final BAT setup.

In order to do this, setup_bats has to move back to asm code, because we
require translation to be enabled to have a stack for C code.  The yucky
thing about that is that the assembler doesn't like ULL so we have to
switch to using HIGH/LOW pairs for physical addresses that are > 32 bits
in length.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Acked-by: York Sun <yorksun@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>