tegra20: enable SPL for tegra20 boards

Add SPL options to tegra20 config files and enable SPL build for
tegra20 boards.  Also remove redundant code from u-boot that is not
contained in SPL.

Signed-off-by: Allen Martin <amartin@nvidia.com>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Tested-by: Thierry Reding <thierry.reding@avionic-design.de>
Signed-off-by: Tom Warren <twarren@nvidia.com>
diff --git a/arch/arm/cpu/armv7/Makefile b/arch/arm/cpu/armv7/Makefile
index 788eada..4fdbee4 100644
--- a/arch/arm/cpu/armv7/Makefile
+++ b/arch/arm/cpu/armv7/Makefile
@@ -32,7 +32,7 @@
 COBJS	+= cpu.o
 COBJS	+= syslib.o
 
-ifneq ($(CONFIG_AM33XX)$(CONFIG_OMAP44XX)$(CONFIG_OMAP54XX),)
+ifneq ($(CONFIG_AM33XX)$(CONFIG_OMAP44XX)$(CONFIG_OMAP54XX)$(CONFIG_TEGRA20),)
 SOBJS	+= lowlevel_init.o
 endif