drivers/pc80/mc146818rtc: Assume we always have ALTCENTURY

This patch has a rather twisted history. It was originally split off
from a chromium patch, which moved ALTCENTURY to Kconfig. However,
since we have no user without ALTCENTURY, we've agreed that the best
way to proceed is to eliminate the non-ALTCENTURY case entirely.

The old commit message and identifiers are kept below for reference:

The availability of "ALTCENTURY" is now set through a kconfig
variable so it can be available to the RTC driver without having to have a
specialized interface.

BUG=None
TEST=Built and booted on Link with the event log code modified to use the RTC
interface. Verified that the event times were accurate.
BRANCH=nyan

Original-Change-Id: Ifa807898e583254e57167fd44932ea86627a02ee
Original-Signed-off-by: Gabe Black <gabeblack@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/197795
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Original-Tested-by: Gabe Black <gabeblack@chromium.org>
Original-Commit-Queue: Gabe Black <gabeblack@chromium.org>

This is the second half the following patch.
(cherry picked from commit 9e0fd75142d29afe34f6c6b9ce0099f478ca5a93)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I8e871f31c3d4be7676abf9454ca90808d1ddca03
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/7987
Reviewed-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Tested-by: build bot (Jenkins)

src/include/rtc.h

@@ -31,7 +31,7 @@ struct rtc_time
 	int wday;
 };
 
-int rtc_set(const struct rtc_time *time, u8 has_century);
-int rtc_get(struct rtc_time *time, u8 has_century);
+int rtc_set(const struct rtc_time *time);
+int rtc_get(struct rtc_time *time);
 
 #endif /* _RTC_H_ */