Some boards might not have RTC xtal, so RTC shouldn't really be
enabled by default. Enable it in the required board files.
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Reviewed-by: NTomasz Figa <t.figa@samsung.com>
Signed-off-by: NKukjin Kim <kgene.kim@samsung.com>