[MIPS] ret_from_irq adjustment

Make sure that RA on top of interrupt stack is an address of ret_from_irq,
so that dump_stack etc. can trace info interrupted context.

Also this patch fixes except_vec_vi_handler and __smtc_ipi_vector which
seems broken.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/smtc-asm.S b/arch/mips/kernel/smtc-asm.S
index 76cb31d..1cb9441 100644
--- a/arch/mips/kernel/smtc-asm.S
+++ b/arch/mips/kernel/smtc-asm.S
@@ -97,15 +97,12 @@
 	SAVE_ALL
 	CLI
 	TRACE_IRQS_OFF
-	move	a0,sp
 	/* Function to be invoked passed stack pad slot 5 */
 	lw	t0,PT_PADSLOT5(sp)
 	/* Argument from sender passed in stack pad slot 4 */
-	lw	a1,PT_PADSLOT4(sp)
-	jalr	t0
-	nop
-	j	ret_from_irq
-	nop
+	lw	a0,PT_PADSLOT4(sp)
+	PTR_LA	ra, _ret_from_irq
+	jr	t0
 
 /*
  * Called from idle loop to provoke processing of queued IPIs