usb: phy: Add driver for USB PHY on QTI emulation platform

Add support for the various USB PHYs used on Qualcomm Technologies,
Inc. emulation platforms. This driver supports simple initialization
via a sequence specified in device tree.

Change-Id: I95cf90d8db04694d26876657e02fd60c22bf4627
Signed-off-by: Jack Pham <jackp@codeaurora.org>