usb: phy: msm: Add HSPHY and SSPHY drivers

Separate out HSPHY and SSPHY specific operations from the DWC3 MSM
driver into their own PHY drivers. This decouples the controller
and glue logic from PHY-specific operations. This will allow for the
possibility of supporting different combinations of controller and
PHY variants without modifying the glue layer.

Change-Id: I2bf5911c3da37e7b278fee33b8a0109466eb46ae
Signed-off-by: Jack Pham <jackp@codeaurora.org>