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>

configs/wandboard_defconfig

@@ -0,0 +1,6 @@
+CONFIG_SPL=y
+CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=arch/arm/imx-common/spl_sd.cfg,MX6QDL"
+CONFIG_ARM=y
+CONFIG_TARGET_WANDBOARD=y
+CONFIG_DM=y
+CONFIG_DM_THERMAL=y

configs/wandboard_dl_defconfig

@@ -1,3 +0,0 @@
-CONFIG_ARM=y
-CONFIG_TARGET_WANDBOARD=y
-CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/boundary/nitrogen6x/nitrogen6dl.cfg,MX6DL,DDR_MB=1024"

configs/wandboard_quad_defconfig

@@ -1,3 +0,0 @@
-CONFIG_ARM=y
-CONFIG_TARGET_WANDBOARD=y
-CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/boundary/nitrogen6x/nitrogen6q2g.cfg,MX6Q,DDR_MB=2048"

configs/wandboard_solo_defconfig

@@ -1,3 +0,0 @@
-CONFIG_ARM=y
-CONFIG_TARGET_WANDBOARD=y
-CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/boundary/nitrogen6x/nitrogen6s.cfg,MX6S,DDR_MB=512"