TI: ARCH_OMAP2PLUS: Enable SPL_STACK_R and provide default value

On ARCH_OMAP2PLUS platforms we know what the DDR layout is going to be,
and that it is safe to use SPL_STACK_R and provide a default value for
it.  select this and re-sync the defconfigs.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index bb64b9c..fca23b4 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -588,6 +588,7 @@
 	bool "TI OMAP2+"
 	select CPU_V7
 	select SPL_BOARD_INIT if SPL
+	select SPL_STACK_R if SPL
 	select SUPPORT_SPL
 	imply FIT