boot/arm-trusted-firmware: add missing qstrip

Add missing qstrip wrapping to the new
BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_TARGETS option.

Signed-off-by: Francois Gervais <fgervais@distech-controls.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

boot/arm-trusted-firmware/arm-trusted-firmware.mk

@@ -140,7 +140,7 @@ endef
 endif
 
 ARM_TRUSTED_FIRMWARE_MAKE_TARGETS += \
-	$(BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_TARGETS)
+	$(call qstrip,$(BR2_TARGET_ARM_TRUSTED_FIRMWARE_ADDITIONAL_TARGETS))
 
 define ARM_TRUSTED_FIRMWARE_BUILD_CMDS
 	$(ARM_TRUSTED_FIRMWARE_BUILD_FIPTOOL)