Enable RGMII connected Quantenna module on MT7621.\\ \\ The Mitrastar designed ZyXEL WAP6805 has a Quantenna QV840\\ module connected to the RGMII pins of the MT7621 SoC. For\\ unknown reasons, it is necessary to change the value of\\ the register at 0x1e110008 from default (usually 0xc000c)\\ to 0x9000c for this connection wo work.\\ \\ This driver simply does that without much fuzz.\\ \\