boot/uboot/uboot.mk: Strip quotes from BR2_TARGET_UBOOT_SPL_NAME

Remove the quotes from the BR2_TARGET_UBOOT_SPL_NAME variable.

Signed-off-by: Jörg Krause <jkrause@posteo.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

boot/uboot/uboot.mk

@@ -127,7 +127,7 @@ endef
 define UBOOT_INSTALL_IMAGES_CMDS
 	cp -dpf $(@D)/$(UBOOT_BIN) $(BINARIES_DIR)/
 	$(if $(BR2_TARGET_UBOOT_SPL),
-		cp -dpf $(@D)/$(BR2_TARGET_UBOOT_SPL_NAME) $(BINARIES_DIR)/)
+		cp -dpf $(@D)/$(call qstrip,$(BR2_TARGET_UBOOT_SPL_NAME)) $(BINARIES_DIR)/)
 	$(if $(BR2_TARGET_UBOOT_ENVIMAGE),
 		$(HOST_DIR)/usr/bin/mkenvimage -s $(BR2_TARGET_UBOOT_ENVIMAGE_SIZE) \
 		$(if $(BR2_TARGET_UBOOT_ENVIMAGE_REDUNDANT),-r) \