phy: qcom-qmp-combo: fix sc8280xp PCS_USB offset

phy: qcom-qmp-combo: fix sc8280xp PCS_USB offset

The PCS_USB register block lives at an offset of 0x300 from the PCS
region on SC8280XP so add the missing offset to avoid corrupting
unrelated registers on runtime suspend.

Note that this region should probably be described separately in the
binding.

Fixes: a2e927b0e50d ("phy: qcom-qmp-combo: Add sc8280xp USB/DP combo phys")
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20220919095700.2228-1-johan+linaro@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>