arm: rmobile: Add SILK board support

SILK is an entry level development board based on R-Car E2 SoC (R8A7794)

This commit supports the following peripherals:
- SCIF, I2C, Ethernet, QSPI, MMC, USB Host

Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Reviewed-by: Tom Rini <trini@ti.com>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/arch/arm/cpu/armv7/rmobile/Kconfig b/arch/arm/cpu/armv7/rmobile/Kconfig
index 6d94199..3586650 100644
--- a/arch/arm/cpu/armv7/rmobile/Kconfig
+++ b/arch/arm/cpu/armv7/rmobile/Kconfig
@@ -21,6 +21,9 @@
 config TARGET_ALT
 	bool "Alt board"
 
+config TARGET_SILK
+	bool "Silk board"
+
 endchoice
 
 config SYS_SOC
@@ -28,7 +31,7 @@
 
 config RMOBILE_EXTRAM_BOOT
 	bool "Enable boot from RAM"
-	depends on TARGET_ALT || TARGET_KOELSCH || TARGET_LAGER
+	depends on TARGET_ALT || TARGET_KOELSCH || TARGET_LAGER || TARGET_SILK
 	default n
 
 source "board/atmark-techno/armadillo-800eva/Kconfig"
@@ -37,5 +40,6 @@
 source "board/renesas/lager/Kconfig"
 source "board/kmc/kzm9g/Kconfig"
 source "board/renesas/alt/Kconfig"
+source "board/renesas/silk/Kconfig"
 
 endif