dt-bindings: phy: spacemit: Introduce PCIe PHY

dt-bindings: phy: spacemit: Introduce PCIe PHY

Add the Device Tree binding for two PCIe PHYs present on the SpacemiT
K1 SoC.  These PHYs are dependent on a separate combo PHY, which
determines at probe time the calibration values used by the PCIe-only
PHYs.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Alex Elder <elder@riscstar.com>
Link: https://lore.kernel.org/all/ba532f8d-a452-40e5-af46-b58b89f70a92@linaro.org/
Tested-by: Yixun Lan <dlan@gentoo.org>
Link: https://patch.msgid.link/20251218151235.454997-3-elder@riscstar.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>