common/board_f.c: align m68k arch to use CONFIG_DISPLAY_CPUINFO

Change all coldfire arch files to use CONFIG_DISPLAY_CPUINFO.

Signed-off-by: Angelo Dureghello <angelo@sysam.it>
Reviewed-by: Tom Rini <trini@konsulko.com>
---
Changes for v2:
   - update common/Kconfig to add M68K to the default y list