usb: gadget: tegra-xudc: Remove usb-role-switch support

Padctl driver will act as a central driver to receive USB role changes via
usb-role-switch. This is updated to corresponding host, device drivers.
Hence remove usb-role-switch from XUDC driver.

Signed-off-by: Nagarjuna Kristam <nkristam@nvidia.com>
Acked-by: Felipe Balbi <balbi@kernel.org>
[treding@nvidia.com: rebase onto Greg's usb-next branch]
Signed-off-by: Thierry Reding <treding@nvidia.com>