Convert CONFIG_AT91_EFLASH to Kconfig

This converts the following to Kconfig:
   CONFIG_AT91_EFLASH

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Acked-by: Eugen Hristev <eugen.hristev@microchip.com>
diff --git a/arch/arm/mach-at91/Kconfig b/arch/arm/mach-at91/Kconfig
index 4448ca1..00f3104 100644
--- a/arch/arm/mach-at91/Kconfig
+++ b/arch/arm/mach-at91/Kconfig
@@ -302,6 +302,14 @@
 config SYS_SOC
 	default "at91"
 
+config AT91_EFLASH
+	bool "Support AT91 flash driver"
+	depends on AT91SAM9XE
+	select USE_SYS_MAX_FLASH_BANKS
+	help
+	  Enable the driver for the embedded flash used in the Atmel
+	  AT91SAM9XE devices.
+
 source "board/atmel/at91sam9260ek/Kconfig"
 source "board/atmel/at91sam9261ek/Kconfig"
 source "board/atmel/at91sam9263ek/Kconfig"