uboot-sunxi: fix build of HAOYU Electronics Marsboard A10

The uboot target is named MarsBoard_A10 and it was not build at all.
This fixes a build problem seen by the build bot.

Fixes: 6a3565985f ("sunxi: Added profile for HAOYU Electronics Marsboard A10")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

package/boot/uboot-sunxi/Makefile

@@ -96,7 +96,7 @@ define U-Boot/Hummingbird_A31
   NAME:=Hummingbird A31 board
 endef
 
-define U-Boot/Marsboard
+define U-Boot/Marsboard_A10
   BUILD_SUBTARGET:=cortexa8
   NAME:=Marsboard
   BUILD_DEVICES:=sun4i-a10-marsboard
@@ -189,6 +189,7 @@ UBOOT_TARGETS := \
 	Cubieboard2 \
 	Cubietruck \
 	Hummingbird_A31 \
+	Marsboard_A10 \
 	Mele_M9 \
 	OLIMEX_A13_SOM \
 	Linksprite_pcDuino \