lantiq: remove vmmc node from FritzBox 7412 dts

As described in commit commit 891a7007598d ("lantiq: enable second VPE
on Fritz!Box 7412"):

 The AVM Fritz!Box 7412 does not use the VMMC part of the Lantiq chip but
 rather a proprietary solution based on the DECT chip for the FXS ports.

We can remove last traces of vmmc in dts.

Signed-off-by: Aleksander Jan Bajkowski <A.Bajkowski@stud.elka.pw.edu.pl>

target/linux/lantiq/files-5.4/arch/mips/boot/dts/lantiq/vr9_avm_fritz7412.dts

@@ -212,7 +212,3 @@
 		};
 	};
 };
-
-&vmmc {
-	status = "okay";
-};