usb: host: tegra: Tegra30 support

The Tegra30 EHCI controller is mostly compatible with the Tegra20
controller, except Tegra30 includes the HOSTPC register extension.
The has_hostpc capability bit must be set in the ehci_hcd structure if
the controller has such extensions. The new tegra_ehci_soc_config
structure is added to describe the differences between the SoCs.

Signed-off-by: Tuomas Tynkkynen <ttynkkynen@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>