POWERPC 86xx: Move BAT setup code to C

This is needed because we will be possibly be locating
devices at physical addresses above 32bits, and the asm
preprocessing does not appear to deal with ULL constants
properly. We now call write_bat in lib_ppc/bat_rw.c.

Signed-off-by: Becky Bruce <becky.bruce@freescale.com>
Acked-by: Jon Loeliger <jdl@freescale.com>