Rename 'mdio-mux-emi1' to 'mdio-mux@54'.

Add fallback compatible string mdio-mux.

Fix below warning:
  arch/arm/boot/dts/nxp/ls/ls1021a-qds.dtb: memory-controller@1530000 (fsl,ifc): board-control@3,0: 'oneOf' conditional failed, one must be fixed:
        'bank-width', 'device-width', 'mdio-mux-emi1' do not match any of the regexes: '^mdio-mux@[a-f0-9,]+$', 'pinctrl-[0-9]+'

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
 arch/arm/boot/dts/nxp/ls/ls1021a-qds.dts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/boot/dts/nxp/ls/ls1021a-qds.dts b/arch/arm/boot/dts/nxp/ls/ls1021a-qds.dts
index 8bc8ff2e3b03d6eeb43d79fe0555842536ab735c..a880875ced83e10c37a4d49d9b9951cd3d458ff0 100644
--- a/arch/arm/boot/dts/nxp/ls/ls1021a-qds.dts
+++ b/arch/arm/boot/dts/nxp/ls/ls1021a-qds.dts
@@ -211,8 +211,8 @@ fpga: board-control@3,0 {
 		device-width = <1>;
 		ranges = <0 3 0 0x100>;
 
-		mdio-mux-emi1 {
-			compatible = "mdio-mux-mmioreg";
+		mdio-mux@54 {
+			compatible = "mdio-mux-mmioreg", "mdio-mux";
 			mdio-parent-bus = <&mdio0>;
 			#address-cells = <1>;
 			#size-cells = <0>;

-- 
2.34.1