usb: host: tegra: Remove leftover code

ehci-tegra calls devm_usb_get_phy, which will never succeed since the Tegra
PHY does not register itself with the PHY subsystem. It is also completely
redundant since the code has already located a PHY via an internal API.

Call otg_set_host unconditionally to simplify the code since it should
be safe to do so.

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