tests: patch: shellcheck: ignore unused functions

Same story as SC2317, the way tests are structured and called
confuses shellcheck.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

tests/patch/shellcheck/shellcheck.sh

@@ -5,7 +5,8 @@ HEAD=$(git rev-parse HEAD)
 rc=0
 
 # SC2317 = unreachable code, gets confused by test case definitions
-SC_FLAGS="-x -e SC2317"
+# SC2329 = function not invoked, gets confused by test case definitions
+SC_FLAGS="-x -e SC2317 -e SC2329"
 
 pr() {
     echo " ====== $* ======" | tee -a /dev/stderr