sbc8548: correct local bus SDRAM size from 64M to 128M

sbc8548: correct local bus SDRAM size from 64M to 128M

The size of the LB SDRAM on this board is 128MB, spanning CS3
and CS4.  It was previously only being configured for 64MB on
CS3, since that was what the original codebase of the MPC8548CDS
had.  In addition to setting up BR4/OR4, this also adds the TLB
entry for the second half of the SDRAM.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>