cifs: clean up call to cifs_dfs_release_automount_timer()

Take the #ifdef junk out of the code, and turn it into a noop macro
when CONFIG_CIFS_DFS_UPCALL isn't defined.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>