binder: fix handling of misaligned binder object

commit 26528be6720bb40bc8844e97ee73a37e530e9c5e upstream.

Fixes crash found by syzbot:
kernel BUG at drivers/android/binder_alloc.c:LINE! (2)

Reported-and-tested-by:  <syzbot+55de1eb4975dec156d8f@syzkaller.appspotmail.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: stable <stable@vger.kernel.org> # 5.0, 4.19, 4.14
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>