Revert "Set DNER for all local fields (#77341)"

This reverts commit 4e85471.

src/coreclr/jit/morph.cpp

@@ -16166,6 +16166,10 @@ void Compiler::fgMorphLocalField(GenTree* tree, GenTree* parent)
             }
             else
             {
+                // There is no existing field that has all the parts that we need
+                // So we must ensure that the struct lives in memory.
+                lvaSetVarDoNotEnregister(lclNum DEBUGARG(DoNotEnregisterReason::LocalField));
+
 #ifdef DEBUG
                 // We can't convert this guy to a float because he really does have his
                 // address taken..
@@ -16174,12 +16178,6 @@ void Compiler::fgMorphLocalField(GenTree* tree, GenTree* parent)
             }
         }
     }
-
-    // If we haven't replaced the field, make sure to set DNER on the local.
-    if (tree->OperIs(GT_LCL_FLD))
-    {
-        lvaSetVarDoNotEnregister(lclNum DEBUGARG(DoNotEnregisterReason::LocalField));
-    }
 }
 
 //------------------------------------------------------------------------