dmx_usb_module: build through KERNEL_MAKE

kmod-usb-serial-dmx_usb_module differs between builds, e.g. on
apm821xx/nand, as dmx_usb.ko carries the absolute path of the kernel
tree:

  /builder/shared-workdir/build/build_dir/.../linux-6.18.52/include/linux/ucopysize.h

The module is built through its own Makefile, which runs
make -C $(KERNELPATH) M=... without any of the OpenWrt prefix maps, and
since Linux 6.13 kbuild includes the kernel headers of external modules
by their absolute path.

That Makefile only wraps kbuild, so call kbuild through $(KERNEL_MAKE)
directly, like the kernel packages of the main repository do. This
passes KERNEL_MAKE_FLAGS and with them ARCH, CROSS_COMPILE and the
prefix maps of the build and staging directories. The options only
used by the wrapper (TARGET, TOOLPREFIX, TOOLPATH, LDOPTS) are dropped.

Signed-off-by: Paul Spooren <mail@aparcar.org>

libs/dmx_usb_module/Makefile

@@ -10,7 +10,7 @@ include $(INCLUDE_DIR)/kernel.mk
 
 PKG_NAME:=dmx_usb_module
 PKG_VERSION:=19.12.1
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://codeload.github.com/lowlander/dmx_usb_module/tar.gz/V$(PKG_VERSION)?
@@ -38,18 +38,8 @@ define KernelPackage/usb-serial-dmx_usb_module/description
 	design and produce its own USB DMX Dongle without paying any licenses.
 endef
 
-DMX_MAKE_OPTS:= -C $(PKG_BUILD_DIR) \
-	PATH="$(TARGET_PATH)" \
-	ARCH="$(LINUX_KARCH)" \
-	CROSS_COMPILE="$(TARGET_CROSS)" \
-	TARGET="$(HAL_TARGET)" \
-	TOOLPREFIX="$(KERNEL_CROSS)" \
-	TOOLPATH="$(KERNEL_CROSS)" \
-	KERNELPATH="$(LINUX_DIR)" \
-	LDOPTS=" "
-
 define Build/Compile
-  $(MAKE) $(DMX_MAKE_OPTS) M=$(PKG_BUILD_DIR)
+	$(KERNEL_MAKE) M="$(PKG_BUILD_DIR)" modules
 endef
 
 $(eval $(call KernelPackage,usb-serial-dmx_usb_module))