phy: qcom: qmp-combo: introduce QMPPHY_MODE

Introduce an enum for the QMP Combo PHY modes, use it in the
QMP commmon phy init function and default to COMBO mode.

Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
[konrad: some renaming and rewording]
Signed-off-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on Lenovo Thinkpad T14S
Link: https://lore.kernel.org/r/20250807-topic-4ln_dp_respin-v4-4-43272d6eca92@oss.qualcomm.com


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