phy: qcom-qmp-usb: clean up power-down handling

phy: qcom-qmp-usb: clean up power-down handling

[ Upstream commit 645d3d04702401e002928b934b830bd25be9e277 ]

Always define the POWER_DOWN_CONTROL register instead of falling back to
the v2 (and v3) offset during power on and power off.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20221017065013.19647-10-johan+linaro@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Stable-dep-of: 922adfd59efd ("phy: qcom-qmp-usb: correct registers layout for IPQ8074 USB3 PHY")
Signed-off-by: Sasha Levin <sashal@kernel.org>