staging: mt7621-pci-phy: dt: bindings: remove bindings txt file

Yaml file for bindings has been properly added. Hence, remove
the old txt file.
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20200410091836.13068-3-sergio.paracuellos@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/mt7621-pci-phy/mediatek,mt7621-pci-phy.txt

-Mediatek Mt7621 PCIe PHY
-
-Required properties:
-- compatible: must be "mediatek,mt7621-pci-phy"
-- reg: base address and length of the PCIe PHY block
-- #phy-cells: must be <1> for pcie0_phy and for pcie1_phy.
-
-Example:
-	pcie0_phy: pcie-phy@1e149000 {
-		compatible = "mediatek,mt7621-pci-phy";
-		reg = <0x1e149000 0x0700>;
-		#phy-cells = <1>;
-	};
-
-	pcie1_phy: pcie-phy@1e14a000 {
-		compatible = "mediatek,mt7621-pci-phy";
-		reg = <0x1e14a000 0x0700>;
-		#phy-cells = <1>;
-	};
-
-	/* users of the PCIe phy */
-
-	pcie: pcie@1e140000 {
-		...
-		...
-		phys = <&pcie0_phy 0>, <&pcie0_phy 1>, <&pcie1_phy 0>;
-		phy-names = "pcie-phy0", "pcie-phy1", "pcie-phy2";
-	};