dt-bindings: phy: qcom,usb-snps-femto-v2: Add SM8250 and SM8350 bindings

Add the compatible strings for the USB2 PHYs found on QCOM
SM8250 & SM8350 SoCs.

Note that the SM8250 compatible is already in use in the dts and
driver implementation but was missing from the documentation.

Signed-off-by: Jack Pham <jackp@codeaurora.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>