phy: qcom-qusb2: Allow specifying default clock scheme

phy: qcom-qusb2: Allow specifying default clock scheme

The TCSR's PHY_CLK_SCHEME register is not available on all SoC
models, but some may still use a differential reference clock.

In preparation for these SoCs, add a se_clk_scheme_default
configuration entry and declare it to true for all currently
supported SoCs (retaining the previous defaults.

This patch brings no functional changes.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210114174718.398638-1-angelogioacchino.delregno@somainline.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>