rtc: Allow use of RTC in SPL and TPL

Add Kconfig options so that the RTC can be used in SPL and TPL. This is
helpful for accessing the contents of CMOS RAM, for example.

Signed-off-by: Simon Glass <sjg@chromium.org>

configs/chromebook_link64_defconfig

@@ -69,6 +69,7 @@ CONFIG_DM_I2C=y
 CONFIG_SYS_I2C_INTEL=y
 CONFIG_CROS_EC=y
 CONFIG_CROS_EC_LPC=y
+CONFIG_SPL_DM_RTC=y
 CONFIG_SYS_NS16550=y
 CONFIG_SPI=y
 CONFIG_SPL_TIMER=y

drivers/rtc/Kconfig

@@ -13,6 +13,24 @@ config DM_RTC
 	  drivers to perform the actual functions. See rtc.h for a
 	  description of the API.
 
+config SPL_DM_RTC
+	bool "Enable Driver Model for RTC drivers in SPL"
+	depends on SPL_DM
+	help
+	  Enable drver model for real-time-clock drivers. The RTC uclass
+	  then provides the rtc_get()/rtc_set() interface, delegating to
+	  drivers to perform the actual functions. See rtc.h for a
+	  description of the API.
+
+config TPL_DM_RTC
+	bool "Enable Driver Model for RTC drivers in TPL"
+	depends on TPL_DM
+	help
+	  Enable drver model for real-time-clock drivers. The RTC uclass
+	  then provides the rtc_get()/rtc_set() interface, delegating to
+	  drivers to perform the actual functions. See rtc.h for a
+	  description of the API.
+
 config RTC_PCF2127
 	bool "Enable PCF2127 driver"
 	depends on DM_RTC

drivers/rtc/Makefile

@@ -4,7 +4,7 @@
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 #ccflags-y += -DDEBUG
 
-obj-$(CONFIG_DM_RTC) += rtc-uclass.o
+obj-$(CONFIG_$(SPL_TPL_)DM_RTC) += rtc-uclass.o
 
 obj-$(CONFIG_RTC_AT91SAM9_RTT) += at91sam9_rtt.o
 obj-y += date.o