sh: remove unused rtc_sh_get/set_time infrastructure

All platforms are now converted to RTC drivers, so this has become
obsolete. The board_time_init() callback still has one caller, but
could otherwise also get killed.

This removes one more usage of the deprecated timespec structure,
which overflows in y2038.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/sh/include/asm/rtc.h

@@ -4,8 +4,6 @@
 
 void time_init(void);
 extern void (*board_time_init)(void);
-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)