net: phy: dp83867: Add TI dp83867 phy

Add support for the TI dp83867 Gigabit ethernet phy
device.

The DP83867 is a robust, low power, fully featured
Physical Layer transceiver with integrated PMD
sublayers to support 10BASE-T, 100BASE-TX and
1000BASE-T Ethernet protocols.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>