dt-bindings: phy: phy-imx8-pcie: Add binding for the pad modes of imx8 pcie phy

Add binding for reference clock PAD modes of the i.MX8 PCIe PHY.

Signed-off-by: Richard Zhu <[e-mail]>
Tested-by: Marcel Ziswiler <[e-mail]>
Reviewed-by: Tim Harvey <[e-mail]>
Tested-by: Tim Harvey <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

include/dt-bindings/phy/phy-imx8-pcie.h

···
+/* SPDX-License-Identifier: (GPL-2.0+ OR MIT) */
+/*
+ * This header provides constants for i.MX8 PCIe.
+ */
+
+#ifndef _DT_BINDINGS_IMX8_PCIE_H
+#define _DT_BINDINGS_IMX8_PCIE_H
+
+/* Reference clock PAD mode */
+#define IMX8_PCIE_REFCLK_PAD_UNUSED	0
+#define IMX8_PCIE_REFCLK_PAD_INPUT	1
+#define IMX8_PCIE_REFCLK_PAD_OUTPUT	2
+
+#endif /* _DT_BINDINGS_IMX8_PCIE_H */