signal/sh: Ensure si_signo is initialized in do_divide_error

Set si_signo.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: linux-sh@vger.kernel.org
Cc: stable@vger.kernel.org
Fixes: 0983b318 ("sh: Wire up division and address error exceptions on SH-2A.")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>