signal/sh: Use force_sig_fault in hw_breakpoint_handler

signal/sh: Use force_sig_fault in hw_breakpoint_handler

The call chain is:
breakpoint
  notify_die
    hw_breakpoint_exceptions_notify
      hw_breakpoint_handler

So the signal number can only be SIGTRAP.

In hw_breakpoint_handler rc is either NOTIFY_STOP or NOTIF_DONE
both of which notifier_to_errno converts to 0.  So si_errno is 0.

Historically si_addr was left unitialized in struct siginfo which is a
bug.  There appears to be no consensus among the various architectures
which value should be in si_addr.  So since no usable value has
been returned up to this point return NULL in si_addr.

Fixes: 4352fc1b12fa ("sh: Abstracted SH-4A UBC support on hw-breakpoint core.")
Fixes: 34d0b5af50a0 ("sh: Convert ptrace to hw_breakpoint API.")
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
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>