Convert CONFIG_RTC_DS1337 et al to Kconfig

This converts the following to Kconfig:
   CONFIG_RTC_DS1337
   CONFIG_RTC_DS1337_NOOSC
   CONFIG_RTC_DS1338
   CONFIG_RTC_DS1374
   CONFIG_RTC_DS3231
   CONFIG_RTC_MC13XXX
   CONFIG_RTC_MXS
   CONFIG_RTC_PT7C4338

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/mx28evk_defconfig b/configs/mx28evk_defconfig
index 996dd5c..dad8839 100644
--- a/configs/mx28evk_defconfig
+++ b/configs/mx28evk_defconfig
@@ -61,6 +61,7 @@
 CONFIG_DM_REGULATOR=y
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_DM_REGULATOR_GPIO=y
+CONFIG_RTC_MXS=y
 CONFIG_CONS_INDEX=0
 CONFIG_SPI=y
 CONFIG_USB=y