uboot-tegra: build with tegra generic subtarget

Fix image build fail by using the generic subtarget.

Fixes: c028e1b1 ("tegra: add generic subtarget")
Ref: 40e3f660 ("uboot-fritz4040: build with ipq40xx generic subtarget")
Signed-off-by: Kuan-Yi Li <[email protected]>
[ add commit description ]
Signed-off-by: Christian Marangi <[email protected]>

package/boot/uboot-tegra/Makefile

@@ -18,6 +18,7 @@ include $(INCLUDE_DIR)/package.mk
 
 define U-Boot/Default
   BUILD_TARGET := tegra
+  BUILD_SUBTARGET := generic
   HIDDEN := y
 endef