phy: phy-mtk-tphy: add support for phy type switch

phy: phy-mtk-tphy: add support for phy type switch

Add support for PHY type switch via the mediatek topmisc syscon.

This is needed on mt7981 to make the PCIe correctly work and display
LinkUp.

Follow the same implementation done on Linux kernel with the usage of
the mediatek,syscon-type property.

Example:

u3port0: usb-phy@11e10700 {
	reg = <0x11e10700 0x900>;
	clocks = <&topckgen CK_TOP_USB3_PHY_SEL>;
	clock-names = "ref";
	#phy-cells = <1>;
	mediatek,syscon-type = <&topmisc 0x218 0>;
	status = "okay";
};

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>