add flash read/write support

arch/arm/src/efm32/Kconfig

@@ -132,6 +132,11 @@ config EFM32_RMU
 	bool "Reset Management Unit (RMU) "
 	default n
 
+config EFM32_FLASHPROG
+	bool "Enable Erase/Write flash function (MSC) "
+	default n
+	select ARCH_HAVE_RAMFUNCS
+
 config EFM32_RMU_DEBUG
 	bool "Reset Management Unit (RMU) DEBUG "
 	default n

arch/arm/src/efm32/Make.defs

@@ -105,6 +105,10 @@ endif
 CHIP_CSRCS  = efm32_start.c efm32_clockconfig.c efm32_irq.c efm32_timerisr.c
 CHIP_CSRCS += efm32_gpio.c efm32_lowputc.c efm32_timer.c efm32_i2c.c
 
+ifeq ($(CONFIG_EFM32_FLASHPROG),y)
+CHIP_CSRCS += efm32_flash.c 
+endif
+
 ifneq ($(CONFIG_ARCH_IDLE_CUSTOM),y)
 CHIP_CSRCS += efm32_idle.c
 endif