dt-bindings: pcie: add entry for PCIe core preset

	Definition: The latency(ms) between when PCIe link is up and before

		any device over the switch is accessed

- qcom,core-preset:

	Usage: optional

	Definition: Determines how aggressive the PCIe PHY equalization is for

		Gen3 cores. The following are recommended settings:

		- short channels: 0x55555555 (default)

		- long channels: 0x77777777

- qcom,pcie-phy-ver:

	Usage: required

	Value type: <u32>

		qcom,ep-latency = <20>;

		qcom,switch-latency = <25>;

		qcom,core-preset = <0x55555555> /* short channel */

		qcom,pcie-phy-ver = <0x2101>; /* v2 version 1.01 */

		qcom,phy-status-offset = <0x814>;

		qcom,phy-status-bit = <6>;