Add the required properties and enable the gmac node for XPI-3128 board.

The minimum reset timing requirements for the phy have been taken from
DP83848J's datasheet [0]

[0] https://www.ti.com/lit/ds/symlink/dp83848j.pdfSigned-off-by: Alex Bee <knaerzche@gmail.com>
Link: https://lore.kernel.org/r/20231202124158.65615-4-knaerzche@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>