ARM: dts: imx6qdl: use MAC-address from nvmem

IMX6QDL has fuse locations specified for storing the MAC for the
built-in ethernet (Table 5-8 in Reference Manual).
Define the fuse location in ocotp and refer to them in fec-ethernet.

If the cells are not flashed, the driver behavior is unchanged, i.e.
other MAC sources will be probed and a random MAC will be used as a
last resort.

Signed-off-by: Nikolaus Voss <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

arch/arm/boot/dts/imx6qdl.dtsi

···
 					 <&clks IMX6QDL_CLK_ENET_REF>;
 				clock-names = "ipg", "ahb", "ptp", "enet_out";
 				fsl,stop-mode = <&gpr 0x34 27>;
+				nvmem-cells = <&fec_mac_addr>;
+				nvmem-cell-names = "mac-address";
 				status = "disabled";
 			};
 
···
 
 				tempmon_temp_grade: temp-grade@20 {
 					reg = <0x20 4>;
+				};
+
+				fec_mac_addr: mac-addr@88 {
+					reg = <0x88 6>;
 				};
 			};