uboot-imx

mpc8260: remove atc board support

These boards are still non-generic boards.

drivers/rtc/ds12887.c should also be removed because it can not
be built without CONFIG_ATC.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Wolfgang Denk <wd@denx.de>