usb: dwc3: Add Qualcomm DWC3 glue layer driver

DWC3 glue layer is hardware layer around Synopsys DesignWare
USB3 core. Its purpose is to supply Synopsys IP with required
clocks, voltages and interface it with the rest of the SoC.

Signed-off-by: Ivan T. Ivanov <iivanov@mm-sol.com>
Signed-off-by: Andy Gross <agross@codeaurora.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>