Simplify arguments to signal handlers on mips.

- Use ksi_addr directly as si_addr in the siginfo instead of the
  'badvaddr' register.
- Remove a duplicate assignment of si_code.
- Use ksi_addr as the 4th argument to the old-style handler instead of
  'badvaddr'.

Reviewed by:	brooks, kevans
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D23013

sys/mips/mips/pm_machdep.c

@@ -147,12 +147,10 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
 		/* fill siginfo structure */
 		sf.sf_si = ksi->ksi_info;
 		sf.sf_si.si_signo = sig;
-		sf.sf_si.si_code = ksi->ksi_code;
-		sf.sf_si.si_addr = (void*)(intptr_t)regs->badvaddr;
 	} else {
 		/* Old FreeBSD-style arguments. */
 		regs->a1 = ksi->ksi_code;
-		regs->a3 = regs->badvaddr;
+		regs->a3 = (uintptr_t)ksi->ksi_addr;
 		/* sf.sf_ahu.sf_handler = catcher; */
 	}