net: usb: asix: validate PHY address before use

In the Linux kernel, the following vulnerability has been resolved:

net: usb: asix: validate PHY address before use

The ASIX driver reads the PHY address from the USB device via asix_read_phy_addr(). A malicious or faulty device can return an invalid address (>= PHY_MAX_ADDR), which causes a warning in mdiobus_get_phy():

addr 207 out of range WARNING: drivers/net/phy/mdio_bus.c:76

Validate the PHY address in asix_read_phy_addr() and remove the now-redundant check in ax88172a.c.