generic: ar8216: do a software reset for switch during hw_init

generic: ar8216: do a software reset for switch during hw_init

This applies to ar8216 and ar8236. QCA's newer U-boot will enable
the switch mdio master for FE switches which makes phy inaccessible
from CPU mdio. (e.g. on TP-Link TL-WR941N v7 Chinese version which
uses QCA9558+AR8236.) For these devices PHY probing is broken and
mdio device probing is a must. We also need to disable switch mdio
master in driver for later PHY initialization.

Do a soft reset during hw_init so that mdio master can be disabled
and expose PHYs to CPU mdio for later PHY accessing.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>