imx: ventana: switch to SPL

Switch to an SPL image. The SPL for Ventana does the following:
 - setup i2c and read the factory programmed EEPROM to obtain DRAM config
   and model for board-specific calibration data
 - configure DRAM per CPU/size/layout/devices/calibration
 - load u-boot.img from NAND and jump to it

This allows for a single SPL+u-boot.img to replace the previous multiple boa
configurations.

Cc: Stefan Roese <sr@denx.de>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Andy Ng <andreas2025@gmail.com>
Cc: Eric Nelson <eric.nelson@boundarydevices.com>
Cc: Tapani Utriainen <tapani@technexion.com>
Cc: Tom Rini <trini@ti.com>

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
diff --git a/board/gateworks/gw_ventana/Makefile b/board/gateworks/gw_ventana/Makefile
index 03bd1fd..33a1788 100644
--- a/board/gateworks/gw_ventana/Makefile
+++ b/board/gateworks/gw_ventana/Makefile
@@ -7,4 +7,5 @@
 #
 
 obj-y  := gw_ventana.o gsc.o eeprom.o
+obj-$(CONFIG_SPL_BUILD) += gw_ventana_spl.o