【openwrt-21.02】openwrt-21.02 T750 按键GPIO自动进入刷机模式功能实现

Openwrt版本

NAME="OpenWrt"
VERSION="21.02-SNAPSHOT"
ID="openwrt"
ID_LIKE="lede openwrt"
PRETTY_NAME="OpenWrt 21.02-SNAPSHOT"
VERSION_ID="21.02-snapshot"
HOME_URL="https://openwrt.org/"
BUG_URL="https://bugs.openwrt.org/"
SUPPORT_URL="https://forum.openwrt.org/"
BUILD_ID="unknown"
OPENWRT_BOARD="mediatek/gem6xx"
OPENWRT_ARCH="arm_cortex-a7"
OPENWRT_TAINTS="no-all busybox"
OPENWRT_DEVICE_MANUFACTURER="OpenWrt"
OPENWRT_DEVICE_MANUFACTURER_URL="https://openwrt.org/"
OPENWRT_DEVICE_PRODUCT="Generic"
OPENWRT_DEVICE_REVISION="v0"
OPENWRT_RELEASE="OpenWrt 21.02-SNAPSHOT