u-boot: unbreak target tools

Got broken by r24697.

target/u-boot/Makefile.in

@@ -21,7 +21,7 @@ U_BOOT_TOOLS:=$(STAGING_DIR)/usr/bin/$(U_BOOT_TOOLS_BIN)
 MKIMAGE:=$(U_BOOT_TOOLS)
 U_BOOT_AUTOSCRIPT=$(BINARIES_DIR)/autoscript
 
-U_BOOT_TARGETS:=$(BINARIES_DIR)/$(U_BOOT_BIN) $(U_BOOT_TOOLS) $(U_BOOT_TARGET_TOOLS)
+U_BOOT_TARGETS:=$(BINARIES_DIR)/$(U_BOOT_BIN) $(U_BOOT_TOOLS)
 
 ifeq ($(strip $(subst ",,$(BR2_TARGET_UBOOT_DEFAULT_ENV))),y)
 #"))
@@ -54,10 +54,10 @@ endif
 
 U_BOOT_TARGET_TOOLS:=
 ifeq ($(BR2_TARGET_UBOOT_TOOL_MKIMAGE),y)
-U_BOOT_TARGET_TOOLS+=$(TARGET_DIR)/usr/bin/mkimage
+U_BOOT_TARGETS+=$(TARGET_DIR)/usr/bin/mkimage
 endif
 ifeq ($(BR2_TARGET_UBOOT_TOOL_ENV),y)
-U_BOOT_TARGET_TOOLS+=$(TARGET_DIR)/usr/sbin/fw_printenv
+U_BOOT_TARGETS+=$(TARGET_DIR)/usr/sbin/fw_printenv
 endif
 
 U_BOOT_CONFIGURE_OPTS :=