[][MT7986a: Fix pwm fan support and update example cooling strategies]

Add pwm fan support to mt7986a
example cooling strategies:
over 125  : reboot
120~125   : notify to driver callback (if callback function is set)
115~120   : FAN 100%
85~115    : FAN 50%
bellow 85 : FAN 0%

You need to connect the 'pwm' pin of PWM FAN to 'PWM1' (GPIO22) pin on mt7986,
and set 'status' properties of 'fan' node in the device tree to enable this.


Change-Id: I220756e5ac8e154251943ca5d6a0303846b40195
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6183410
10 files changed