phy: qcom-qusb2: Add configuration for SDM660

The SDM660 SoC uses the same configuration as MSM8996, but the
clock scheme uses a differential reference clock and none of
the SoCs in this series (630, 636 and others) have got a usable
PHY_CLK_SCHEME register in the TCSR for clk scheme detection.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210114174718.398638-2-angelogioacchino.delregno@somainline.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>