net:phy:motorcomm: support modifying RGMII_TX_CLK delay train from dts

net:phy:motorcomm: support modifying RGMII_TX_CLK delay train from dts

support use original or inverted RGMII_TX_CLK delay train.
10M/100M/1000M can be configured independently.

tx_inverted_xx = val;

for example:
&gmac0 {
    #address-cells = <1>;
    #size-cells = <0>;
    phy0: ethernet-phy@0 {
	    tx_inverted_10 = <0>;
	    tx_inverted_100 = <1>;
	    tx_inverted_1000 = <1>;
    };
};

0: original (default)
1: inverted

Signed-off-by: Samin Guo <samin.guo@starfivetech.com>