wandboard: Switch to SPL support

Currently we need to build one U-boot image for each of the wandboard
variants: quad, dual-lite and solo.

By switching to SPL we can support all these variants with a single binary,
which is very convenient.

Based on the work from Richard Hu.

Tested kernel booting on the three boards.

Signed-off-by: Richard Hu <hakahu@gmail.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Tested-by: Vagrant Cascadian <vagrant@aikidev.net>
Reviewed-by: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 6727423..2f2c0eb 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -499,6 +499,7 @@
 config TARGET_WANDBOARD
 	bool "Support wandboard"
 	select CPU_V7
+	select SUPPORT_SPL
 
 config TARGET_WARP
 	bool "Support WaRP"