armv7, beagle: Second SDRAM bank don;t work

since commit 3667cbee
on beagle board the second sdram bank didn;t longer
work. Since this patch sdram settings just get copied
from bank a, but CMD_NOP, CMD_PRECHARGE, CMD_AUTOREFRESH
are not executed and after that mr register is also
not updated. This patch adds this for the bank b.

Signed-off-by: Heiko Schocher <hs@denx.de>
cc: Steve Sakoman <steve@sakoman.com>
cc: Sandeep Paulraj <s-paulraj@ti.com>
cc: Wolfgang Denk <wd@denx.de>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>