m68k: Fix incorrect memory access on M5235

The csarX and cscrX registers in the fbcs_t struct are 16-bit for
CONFIG_M5235 and 32-bit wide otherwise. The code in cpu_init.c
accessed them always as 32-bit, effectively creating a wrong memory
access on M5235. Fixed that by choosing out_be16/out_be32 depending
on whether CONFIG_M5235 is defined or not.

Cc: Jason Jin <Jason.jin@freescale.com>
Signed-off-by: Vasili Galka <vvv444@gmail.com>