Fix MCF5235 SDRAM base address macro

SDRAMC_DARCn_BA() macro worked fine when the BA is 0x00000000 even
though the macro is incorrect. It causes the BA to be set incorrctly
for other base addresses. This patch fixes the macro so that base
addresses other than zero can be used with the MCF5235.

Signed-off-by: Steve deRosier <derosier@gmail.com>