usb: dwc3: qcom: Add device tree binding

QCOM USB3.0 core wrapper consist of USB3.0 IP from Synopsys
(SNPS) and HS, SS PHY's control and configuration registers.

It could operate in device mode (SS, HS, FS) and host
mode (SS, HS, FS, LS).

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>