ARM: imx: Support larger SPL size on IMX6DQ

Previously the SPL size on all iMX6 platforms was restricted to 68KB
because the OCRAM size on iMX6SL/DL parts is only 128KB. However, the
other iMX6 variants have 256KB of OCRAM. Add an option
CONFIG_MX6_OCRAM_256KB which allows using the full size on boards which
don't need to support the SL/DL variants. This allows for an SPL size of
196KB, which makes it much easier to use configurations such as SPL with
driver model and FDT control.

Signed-off-by: Robert Hancock <hancock@sedsystems.ca>
Tested-by: Adam Ford <aford173@gmail.com> #imx6q_logic
diff --git a/common/spl/Kconfig b/common/spl/Kconfig
index f467eca..2ca2199 100644
--- a/common/spl/Kconfig
+++ b/common/spl/Kconfig
@@ -28,7 +28,8 @@
 config SPL_SIZE_LIMIT
 	int "Maximum size of SPL image"
 	depends on SPL
-	default 69632 if ARCH_MX6
+	default 69632 if ARCH_MX6 && !MX6_OCRAM_256KB
+	default 200704 if ARCH_MX6 && MX6_OCRAM_256KB
 	default 0
 	help
 	  Specifies the maximum length of the U-Boot SPL image.