usb: phy: snps: Put PHY in non-driving mode for charger detection

PMIC charger driver requests PHY to place USB D+/D- lines in hi-Z
state prior to performing charger detection. This is exposed as a
regulator interface. During the enable callback, perform power on
and reset of the PHY and then write to the UTMI override register
to set OPMODE as non-driving.

In the event that a host downstream port is connected, the normal
init sequence will follow and OPMODE will be set to normal due to
the reset.

Change-Id: I630339dd6e0056d36dfb089fbe7eaebe0a13dae8
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>