util_git.sh: Checkout to FETCH_HEAD for refspec in "refs/" format

Same reason as "refs/changes" format as explained in commit a9afdbf [1],
all refspec in "refs/" format cannot be directly used to checkout.
So checkout to FETCH_HEAD for all refspec in "refs/" format.

[1]: https://review.trustedfirmware.org/c/ci/tf-m-ci-scripts/+/22012

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: I30cb3715165d9e84cc52dd88a88cf1439830ff9b
diff --git a/util_git.sh b/util_git.sh
index 4f550b4..0c5d909 100644
--- a/util_git.sh
+++ b/util_git.sh
@@ -46,8 +46,8 @@
         fi
 
         # Checkout to specified refspec
-        if [[ "${REPO_REFSPEC}" =~ "refs/changes" ]]; then
-            # Refspec in "refs/changes" format cannot be directly used to checkout
+        if [[ "${REPO_REFSPEC}" =~ "refs/" ]]; then
+            # Refspec in "refs/" format cannot be directly used to checkout
             git checkout ${REPO_FETCH_HEAD}
         else
             git checkout ${REPO_REFSPEC}