phy: qcom-qmp-ufs: refactor qmp_ufs_power_off

phy: qcom-qmp-ufs: refactor qmp_ufs_power_off

In qmp_ufs_power_off, the PHY is already powered down by asserting
QPHY_PCS_POWER_DOWN_CONTROL. Therefore, additional phy_reset and
stopping SerDes are unnecessary. Also this approach does not
align with the phy HW programming guide.

Thus, refactor qmp_ufs_power_off to remove the phy_reset and stop
SerDes calls to simplify the code and ensure alignment with the PHY
HW programming guide.

Signed-off-by: Nitin Rawat <quic_nitirawa@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20250526153821.7918-10-quic_nitirawa@quicinc.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>