edac: mpc85xx: fix building as a module

including of <asm/mpc85xx.h> causes build problems since it doesn't exist.

Also removed warning:
drivers/edac/mpc85xx_edac.c:45: warning: 'mpc85xx_ctl_name' defined but not used

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Doug Thompson <dougthompson@xmission.com>
Acked-by: Dave Jiang <djiang@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>