Use rtc-rs5c348 and at25 spi protocol driver and spi_txx9 spi
controller driver instead of platform dependent codes.

This patch also removes dependencies to old RTC interfaces such as
rtc_mips_get_time, etc.
Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>