sunxi: enable usbgadget feature

The USB of most sunxi devices works in otg or peripheral mode.
Enable this feature to use usbgadget. Tested on OrangePi Zero3.

Signed-off-by: Chukun Pan <[email protected]>
Link: https://patchwork.ozlabs.org/project/openwrt/patch/[email protected]/
Signed-off-by: Hauke Mehrtens <[email protected]>

target/linux/sunxi/Makefile

@@ -7,7 +7,7 @@ include $(TOPDIR)/rules.mk
 ARCH:=arm
 BOARD:=sunxi
 BOARDNAME:=Allwinner ARM SoCs
-FEATURES:=usb ext4 display rootfs-part rtc squashfs
+FEATURES:=ext4 display rootfs-part rtc squashfs usb usbgadget
 SUBTARGETS:=cortexa8 cortexa7 cortexa53
 
 KERNEL_PATCHVER:=6.6