cifs: remove set but not used variable 'sep'

Fixes gcc '-Wunused-but-set-variable' warning:

fs/cifs/cifs_dfs_ref.c: In function 'cifs_dfs_do_automount':
fs/cifs/cifs_dfs_ref.c:309:7: warning:
 variable 'sep' set but not used [-Wunused-but-set-variable]

It never used since introdution in commit 0f56b277073c ("cifs: Make use
of DFS cache to get new DFS referrals")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Paulo Alcantara <palcantara@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifs_dfs_ref.c

@@ -295,7 +295,6 @@ static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
 	int len;
 	int rc;
 	struct vfsmount *mnt;
-	char sep;
 
 	cifs_dbg(FYI, "in %s\n", __func__);
 	BUG_ON(IS_ROOT(mntpt));
@@ -314,8 +313,6 @@ static struct vfsmount *cifs_dfs_do_automount(struct dentry *mntpt)
 		goto cdda_exit;
 	}
 
-	sep = CIFS_DIR_SEP(cifs_sb);
-
 	/* always use tree name prefix */
 	full_path = build_path_from_dentry_optional_prefix(mntpt, true);
 	if (full_path == NULL)