rtc: rtc-sh: Support 4-digit year on SH7705/SH7710/SH7712.

All SH-4 parts have a 4-digit year, while the SH-3 parts typically
only use a 2-digit one. The SH7705, SH7710, and SH7712 SH-3 parts
however opted to extend it to 4-digit and still look and act like
an SH-3 RTC in all other ways.

This adds a capability flag (RTC_CAP_4_DIGIT_YEAR) that these
corner-case CPU subtypes can set in their platform data and cleans
up some of the ifdef mess in the driver as a result.

Reported-by: Markus Brunner <super.firetwister@gmail.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/include/asm-sh/rtc.h b/include/asm-sh/rtc.h
index 91aacc9..858da99 100644
--- a/include/asm-sh/rtc.h
+++ b/include/asm-sh/rtc.h
@@ -5,4 +5,10 @@
 extern void (*rtc_sh_get_time)(struct timespec *);
 extern int (*rtc_sh_set_time)(const time_t);
 
+#define RTC_CAP_4_DIGIT_YEAR	(1 << 0)
+
+struct sh_rtc_platform_info {
+	unsigned long capabilities;
+};
+
 #endif /* _ASM_RTC_H */