phy: qcom-qmp: pcs: Add v6.20 register offsets

The new SM8550 SoC bumps up the HW version of QMP phy to v6.20 for
PCIE g4x2. Add the new PCS offsets in a dedicated header file.

Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20230208180020.2761766-4-abel.vesa@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>