[SPARK-35829][SQL][FOLLOWUP] Use subExprCode to avoid duplicate call of addNewFunction

### What changes were proposed in this pull request?

A followup of #32980. We should use `subExprCode` to avoid duplicate call of `addNewFunction`.

### Why are the changes needed?

Avoid duplicate all of `addNewFunction`.

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

Existing test.

Closes #33305 from viirya/fix-minor.

Authored-by: Liang-Chi Hsieh <viirya@gmail.com>
Signed-off-by: Liang-Chi Hsieh <viirya@gmail.com>

Author: viirya

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala

@@ -1249,7 +1249,7 @@ class CodegenContext extends Logging {
       // at least two nodes) as the cost of doing it is expected to be low.
 
       val subExprCode = s"${addNewFunction(fnName, fn)}($INPUT_ROW);"
-      subexprFunctions += s"${addNewFunction(fnName, fn)}($INPUT_ROW);"
+      subexprFunctions += subExprCode
       val state = SubExprEliminationState(
         ExprCode(code"$subExprCode",
           JavaCode.isNullGlobal(isNull),