dt-bindings: usb: qcom,dwc3: Add bindings for SM8150, SM8250, SM8350

Add compatible strings for the USB DWC3 controller on QCOM SM8150,
SM8250 and SM8350 SoCs.

Note the SM8150 & SM8250 compatibles are already being used in the
dts but was missing from the documentation.

Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Link: https://lore.kernel.org/r/20210119173748.6729-1-jackp@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>