usb: phy: tegra: Support waking up from a low power mode

Support programming of waking up from a low power mode by implementing the
generic set_wakeup() callback of the USB PHY API.

Tested-by: Matt Merhar <mattmerhar@protonmail.com>
Tested-by: Nicolas Chauvet <kwizart@gmail.com>
Tested-by: Peter Geis <pgwipeout@gmail.com>
Tested-by: Ion Agorria <ion@agorria.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Acked-by: Peter Chen <peter.chen@kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20201218120246.7759-3-digetx@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>