tegra: allow build to succeed with SPL disabled

u-boot-dtb-tegra.bin and u-boot-nodtb-tegra.bin binaries
are generated only if the SPL build is enabled as they have
dependency on SPL build

Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
Signed-off-by: Tom Warren <twarren@nvidia.com>

Makefile

@@ -350,12 +350,14 @@ endif
 
 # enable combined SPL/u-boot/dtb rules for tegra
 ifneq ($(CONFIG_TEGRA),)
+ifeq ($(CONFIG_SPL),y)
 ifeq ($(CONFIG_OF_SEPARATE),y)
 ALL-y += $(obj)u-boot-dtb-tegra.bin
 else
 ALL-y += $(obj)u-boot-nodtb-tegra.bin
 endif
 endif
+endif
 
 build := -f $(TOPDIR)/scripts/Makefile.build -C