u-boot: get rid of version specific patch dirs

All those dirs seem a bit excessive for a single patch

target/u-boot/Makefile.in

@@ -81,7 +81,7 @@ $(U_BOOT_DIR)/.unpacked: $(DL_DIR)/$(U_BOOT_SOURCE)
 	touch $@
 
 $(U_BOOT_DIR)/.patched: $(U_BOOT_DIR)/.unpacked
-	toolchain/patch-kernel.sh $(U_BOOT_DIR) target/u-boot/$(U_BOOT_VERSION) \
+	toolchain/patch-kernel.sh $(U_BOOT_DIR) target/u-boot \
 		u-boot-$(U_BOOT_VERSION)-\*.patch \
 		u-boot-$(U_BOOT_VERSION)-\*.patch.$(ARCH)
 ifneq ($(strip $(U_BOOT_ARCH_PATCH_DIR)),)