dt-bindings: phy-qcom-qusb2: Update binding for QUSB2 V2 version

Update generic compatible string for QUSB2 V2 PHY. This will allow
all targets using QUSB2 V2 use same string.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Reviewed-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>