u-boot: fix custom patch handling

target/u-boot/Makefile.in

@@ -40,7 +40,7 @@ $(U_BOOT_DIR)/.patched: $(U_BOOT_DIR)/.unpacked
 ifneq ($(strip $(BR2_TARGET_UBOOT_CUSTOM_PATCH)),"")
 	@mkdir -p $(U_BOOT_PATCH_DIR)
 	cp -dpr $(BR2_TARGET_UBOOT_CUSTOM_PATCH) $(U_BOOT_PATCH_DIR)
-	toolchain/patch-kernel.sh $(U_BOOT_DIR) $(U_BOOT_PATCH_DIR) *.patch
+	toolchain/patch-kernel.sh $(U_BOOT_DIR) $(U_BOOT_PATCH_DIR) \*.patch
 endif
 	touch $@