usb: host: xhci-tegra: Selectively program IPFS

Starting with Tegra186, the XUSB controller no longer has the IPFS
wrapper. This commit adds a "has_ipfs" field to struct tegra_xusb_soc
that can be used to declare the existence of the IPFS wrapper.

For the existing chips (i.e. Tegra124 and Tegra210), the new field is
set to true. A future patch adding support for Tegra186 will set it to
false.

Signed-off-by: JC Kuo <jckuo@nvidia.com>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>