sandbox: Tidy up RTC options

At present we enable the sandbox RTC driver for all builds. Add a separate
Kconfig option to control this, so that it can be disabled in TPL, where
it is not needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 35b6ed4..fcfda28 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -231,6 +231,24 @@
 	  Enable driver for ST's M41T62 compatible RTC devices (like RV-4162).
 	  It is a serial (I2C) real-time clock (RTC) with alarm.
 
+config RTC_SANDBOX
+	bool "Enable sandbox RTC driver"
+	depends on SANDBOX && DM_RTC
+	default y
+	help
+	  Enable the sandbox RTC driver. This driver connects to the RTC
+	  emulator and is used to test the RTC uclasses and associated code,
+	  as well as the I2C subsystem.
+
+config SPL_RTC_SANDBOX
+	bool "Enable sandbox RTC driver (SPL)"
+	depends on SANDBOX && SPL_DM_RTC
+	default y
+	help
+	  Enable the sandbox RTC driver. This driver connects to the RTC
+	  emulator and is used to test the RTC uclasses and associated code,
+	  as well as the I2C subsystem.
+
 config RTC_STM32
 	bool "Enable STM32 RTC driver"
 	depends on DM_RTC
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 447551e..b6c9029 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -16,7 +16,7 @@
 obj-$(CONFIG_RTC_DS3232) += ds3232.o
 obj-$(CONFIG_RTC_EMULATION) += emul_rtc.o
 obj-$(CONFIG_RTC_HT1380) += ht1380.o
-obj-$(CONFIG_SANDBOX) += i2c_rtc_emul.o
+obj-$(CONFIG_$(SPL_TPL_)RTC_SANDBOX) += i2c_rtc_emul.o
 obj-$(CONFIG_RTC_ISL1208) += isl1208.o
 obj-$(CONFIG_RTC_M41T62) += m41t62.o
 obj-$(CONFIG_RTC_MC13XXX) += mc13xxx-rtc.o
@@ -35,6 +35,6 @@
 obj-$(CONFIG_RTC_RX8010SJ) += rx8010sj.o
 obj-$(CONFIG_RTC_S35392A) += s35392a.o
 obj-$(CONFIG_RTC_STM32) += stm32_rtc.o
-obj-$(CONFIG_SANDBOX) += sandbox_rtc.o
+obj-$(CONFIG_$(SPL_TPL_)RTC_SANDBOX) += sandbox_rtc.o
 obj-$(CONFIG_RTC_ABX80X) += abx80x.o
 obj-$(CONFIG_RTC_ZYNQMP) += zynqmp_rtc.o