This driver uses the century bit of this RTC in the opposite way Linux does.
From Linux's rtc-pcf8563.c:
	/*
	 * The meaning of MO_C bit varies by the chip type.
	 * From PCF8563 datasheet: this bit is toggled when the years
	 * register overflows from 99 to 00
	 *   0 indicates the century is 20xx
	 *   1 indicates the century is 19xx
	 * From RTC8564 datasheet: this bit indicates change of
	 * century. When the year digit data overflows from 99 to 00,
	 * this bit is set. By presetting it to 0 while still in the
	 * 20th century, it will be set in year 2000, ...
	 * There seems no reliable way to know how the system use this
	 * bit.  So let's do it heuristically, assuming we are live in
	 * 1970...2069.
	 */

As U-Boot's PCF8563 driver does not say it is supposed to support the RTC8564,
make this driver compatible with Linux's by giving the opposite meaning to the
century bit.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Cc: Wolfgang Denk <wd@denx.de>

Signed-off-by: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Acked-by: Stefan Roese <sr@denx.de>

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>

Signed-off-by: Michal Simek <monstr@monstr.eu>

Modify the RTC API to provide one a status for the time reported by
the rtc_get() function:
  0 - a reliable time is guaranteed,
< 0 - a reliable time isn't guaranteed (power fault, clock issues,
      and so on).

The RTC chip drivers are responsible for providing this info if the
corresponding chip supports such functionality. If not - always
report that the time is reliable.

The POST RTC test was modified to detect the RTC faults utilizing
this new rtc_get() feature.

Signed-off-by: Yuri Tikhonov <yur@emcraft.com>

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>