mediatek: build USB XHCI support as module

Instead of always including the XHCI driver in the kernel on all
MediaTek boards, selectively include the kernel module only on boards
which actually make use of USB functionality.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

package/kernel/linux/modules/usb.mk

@@ -1746,6 +1746,7 @@ define KernelPackage/usb3
 	+TARGET_bcm53xx:kmod-usb-bcma \
 	+TARGET_bcm53xx:kmod-phy-bcm-ns-usb3 \
 	+TARGET_ramips_mt7621:kmod-usb-xhci-mtk \
+	+TARGET_mediatek:kmod-usb-xhci-mtk \
 	+TARGET_apm821xx_nand:kmod-usb-xhci-pci-renesas \
 	+TARGET_mvebu_cortexa9:kmod-usb-xhci-pci-renesas
   KCONFIG:= \

target/linux/mediatek/filogic/config-5.15

@@ -412,12 +412,7 @@ CONFIG_TREE_SRCU=y
 CONFIG_UBIFS_FS=y
 # CONFIG_UCLAMP_TASK is not set
 # CONFIG_UNMAP_KERNEL_AT_EL0 is not set
-CONFIG_USB=y
-CONFIG_USB_COMMON=y
 CONFIG_USB_SUPPORT=y
-CONFIG_USB_XHCI_HCD=y
-CONFIG_USB_XHCI_MTK=y
-# CONFIG_USB_XHCI_PLATFORM is not set
 CONFIG_VMAP_STACK=y
 CONFIG_WATCHDOG_CORE=y
 CONFIG_WATCHDOG_PRETIMEOUT_DEFAULT_GOV_PANIC=y

target/linux/mediatek/mt7622/config-5.15

@@ -441,12 +441,7 @@ CONFIG_TREE_SRCU=y
 CONFIG_UBIFS_FS=y
 # CONFIG_UCLAMP_TASK is not set
 # CONFIG_UNMAP_KERNEL_AT_EL0 is not set
-CONFIG_USB=y
-CONFIG_USB_COMMON=y
 CONFIG_USB_SUPPORT=y
-CONFIG_USB_XHCI_HCD=y
-CONFIG_USB_XHCI_MTK=y
-# CONFIG_USB_XHCI_PLATFORM is not set
 CONFIG_VMAP_STACK=y
 CONFIG_WATCHDOG_CORE=y
 CONFIG_WATCHDOG_PRETIMEOUT_DEFAULT_GOV_PANIC=y

target/linux/mediatek/mt7623/config-5.15

@@ -552,9 +552,6 @@ CONFIG_USB_ROLE_SWITCH=y
 CONFIG_USB_SUPPORT=y
 CONFIG_USB_U_ETHER=y
 CONFIG_USB_U_SERIAL=y
-CONFIG_USB_XHCI_HCD=y
-CONFIG_USB_XHCI_MTK=y
-CONFIG_USB_XHCI_PLATFORM=y
 CONFIG_USE_OF=y
 CONFIG_VFP=y
 CONFIG_VFPv3=y