Add support for the AP135 2.0 reference platform.

This is a QCA9558 SoC (2ghz 3x3) with an atheros 11ac PCIe 5GHz 3x3
NIC and an AR8327 gigabit ethernet switch.

TODO:

• The AR8327 gigabit switch support bugfixes are forthcoming.
• 11ac support and 11ac NIC support