phy: qcom-qmp-usb: make QPHY_PCS_MISC_CLAMP_ENABLE access conditional

phy: qcom-qmp-usb: make QPHY_PCS_MISC_CLAMP_ENABLE access conditional

The register QPHY_V[34]_PCS_MISC_CLAMP_ENABLE is present only on some
SoC families. Other platforms (qcm2290) can have PCS_MISC region, but do
not have this register. Add it to the register layout table and check
that it is defined before toggling CLAMP settings.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20230824211952.1397699-5-dmitry.baryshkov@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>