rtc: s5m-rtc: add real-time clock driver for s5m8767

Add real-time clock driver for s5m8767.

Signed-off-by: Sangbeom Kim <sbkim73@samsung.com>
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Todd Broch <tbroch@chromium.org>
Cc: Mark Brown <broonie@kernel.org>
Acked-by: Lee Jones <lee.jones@linaro.org>	[mfd parts]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>