phy: qcom-qmp: Add msm8998 PCIe QMP PHY support

Documentation for this PHY, and the proper configuration settings,
is *not* publicly available. Therefore the initialization sequence
is copied wholesale from downstream:

https://source.codeaurora.org/quic/la/kernel/msm-4.4/tree/arch/arm/boot/dts/qcom/msm8998-v2.dtsi?h=LE.UM.1.3.r3.25#n372



Reviewed-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Signed-off-by: Marc Gonzalez <marc.w.gonzalez@free.fr>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>