net: phy: add Broadcom BCM7xxx internal PHY driver

This patch adds support for the Broadcom BCM7xxx Set Top Box SoCs
internal PHYs. This driver supports the following generation of SoCs:

- BCM7366, BCM7439, BCM7445 (28nm process)
- all 40nm and 65nm (older MIPS-based SoCs)

The PHYs on these SoCs require a bunch of workarounds to operate
correctly, both during configuration time and at suspend/resume time,
the driver handles that for us.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>