[MIPS] Generate SIGILL again

    
The rdhwr emulation accidentally swallowed the SIGILL from most other
illegal instructions.  Make sure to return -EFAULT by default.
Signed-off-by: NDaniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/kernel/traps.c

@@ -534,13 +534,14 @@ static inline int simulate_rdhwr(struct pt_regs *regs)
 		switch (rd) {
 			case 29:
 				regs->regs[rt] = ti->tp_value;
-				break;
+				return 0;
 			default:
 				return -EFAULT;
 		}
 	}
 
-	return 0;
+	/* Not ours.  */
+	return -EFAULT;
 }
 
 asmlinkage void do_ov(struct pt_regs *regs)