usb: phy: add support for QMP PHY

A new PHY (QMP PHY) is introduced on krypton for supporting USB SS.
Since the DWC3 driver requires the definition of both HS and SS PHYs
the basic framework of QMP PHY is added.
The specific sequences will be added at a later stage.

Change-Id: I885c2c0adea926ef60003b68727370d0eb60e0f1
Signed-off-by: Maya Erez <merez@codeaurora.org>