Documentation: dts: xgene: Add TX/RX delay field

Optional properties:

- status: Should be "ok" or "disabled" for enabled/disabled. Default is "ok".

- tx-delay: Delay value for RGMII bridge TX clock.

	    Valid values are between 0 to 7, that maps to

	    417, 717, 1020, 1321, 1611, 1913, 2215, 2514 ps

	    Default value is 4, which corresponds to 1611 ps

- rx-delay: Delay value for RGMII bridge RX clock.

	    Valid values are between 0 to 7, that maps to

	    273, 589, 899, 1222, 1480, 1806, 2147, 2464 ps

	    Default value is 2, which corresponds to 899 ps

Example:

	menetclk: menetclk {

/* Board-specific peripheral configurations */

&menet {

	tx-delay = <4>;

	rx-delay = <2>;

        status = "ok";

};