net: phy: micrel: Add support for LAN8804 PHY

The LAN8804 PHY has same features as that of LAN8814 PHY except that it
doesn't support 1588, SyncE or Q-USGMII.

This PHY is found inside the LAN966X switches.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>