usb: phy: tegra: Keep track of power on-off state

usb: phy: tegra: Keep track of power on-off state

The PHY driver should keep track of the enable state, otherwise enable
refcount is screwed if USB driver tries to enable PHY when it is already
enabled. This will be the case for ChipIdea and Tegra EHCI drivers once
PHY driver will gain support for the init/shutdown callbacks.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20200106013416.9604-5-digetx@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>