MPC85xx BA bits not set for 3-bit bank address DIMM

The current implementation does not set the number of bank address bits
(BA) in the processor. The default assumes 2 logical bank bits. This
works fine for a DIMM that uses devices with 4 internal banks (SPD
byte17 = 0x4) but needs to be set appropriately for a DIMM that uses
devices with 8 internal banks (SPD byte17 = 0x8).

Signed-off-by: Greg Davis <DavisG@embeddedplanet.com>