applications/solvers: Moved createMRF.H into createField.H

to ensure MRF functionality is available for the -postProcess option

applications/solvers/basic/potentialFoam/createFields.H

@@ -97,3 +97,5 @@ setRefCell
     PhiRefValue
 );
 mesh.setFluxRequired(Phi.name());
+
+#include "createMRF.H"

applications/solvers/basic/potentialFoam/potentialFoam.C

@@ -79,7 +79,6 @@ int main(int argc, char *argv[])
     pisoControl potentialFlow(mesh, "potentialFlow");
 
     #include "createFields.H"
-    #include "createMRF.H"
 
     // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //