microblaze: Fix stack usage in interrupt handler

Do not save registers below r1 stack pointer because
it is not checked by stack undeflow is not able to detect
it.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/cpu/irq.S

@@ -11,71 +11,70 @@
 	.text
 	.global _interrupt_handler
 _interrupt_handler:
-	swi	r2, r1, -4
-	swi	r3, r1, -8
-	swi	r4, r1, -12
-	swi	r5, r1, -16
-	swi	r6, r1, -20
-	swi	r7, r1, -24
-	swi	r8, r1, -28
-	swi	r9, r1, -32
-	swi	r10, r1, -36
-	swi	r11, r1, -40
-	swi	r12, r1, -44
-	swi	r13, r1, -48
-	swi	r14, r1, -52
-	swi	r15, r1, -56
-	swi	r16, r1, -60
-	swi	r17, r1, -64
-	swi	r18, r1, -68
-	swi	r19, r1, -72
-	swi	r20, r1, -76
-	swi	r21, r1, -80
-	swi	r22, r1, -84
-	swi	r23, r1, -88
-	swi	r24, r1, -92
-	swi	r25, r1, -96
-	swi	r26, r1, -100
-	swi	r27, r1, -104
-	swi	r28, r1, -108
-	swi	r29, r1, -112
-	swi	r30, r1, -116
-	swi	r31, r1, -120
 	addik	r1, r1, -124
+	swi	r2, r1, 4
+	swi	r3, r1, 8
+	swi	r4, r1, 12
+	swi	r5, r1, 16
+	swi	r6, r1, 20
+	swi	r7, r1, 24
+	swi	r8, r1, 28
+	swi	r9, r1, 32
+	swi	r10, r1, 36
+	swi	r11, r1, 40
+	swi	r12, r1, 44
+	swi	r13, r1, 48
+	swi	r14, r1, 52
+	swi	r15, r1, 56
+	swi	r16, r1, 60
+	swi	r17, r1, 64
+	swi	r18, r1, 68
+	swi	r19, r1, 72
+	swi	r20, r1, 76
+	swi	r21, r1, 80
+	swi	r22, r1, 84
+	swi	r23, r1, 88
+	swi	r24, r1, 92
+	swi	r25, r1, 96
+	swi	r26, r1, 100
+	swi	r27, r1, 104
+	swi	r28, r1, 108
+	swi	r29, r1, 112
+	swi	r30, r1, 116
+	swi	r31, r1, 120
 	brlid	r15, interrupt_handler
 	nop
+	lwi	r31, r1, 120
+	lwi	r30, r1, 116
+	lwi	r29, r1, 112
+	lwi	r28, r1, 108
+	lwi	r27, r1, 104
+	lwi	r26, r1, 100
+	lwi	r25, r1, 96
+	lwi	r24, r1, 92
+	lwi	r23, r1, 88
+	lwi	r22, r1, 84
+	lwi	r21, r1, 80
+	lwi	r20, r1, 76
+	lwi	r19, r1, 72
+	lwi	r18, r1, 68
+	lwi	r17, r1, 64
+	lwi	r16, r1, 60
+	lwi	r15, r1, 56
+	lwi	r14, r1, 52
+	lwi	r13, r1, 48
+	lwi	r12, r1, 44
+	lwi	r11, r1, 40
+	lwi	r10, r1, 36
+	lwi	r9, r1, 32
+	lwi	r8, r1, 28
+	lwi	r7, r1, 24
+	lwi	r6, r1, 20
+	lwi	r5, r1, 16
+	lwi	r4, r1, 12
+	lwi	r3, r1, 8
+	lwi	r2, r1, 4
 	addik	r1, r1, 124
-	lwi	r31, r1, -120
-	lwi	r30, r1, -116
-	lwi	r29, r1, -112
-	lwi	r28, r1, -108
-	lwi	r27, r1, -104
-	lwi	r26, r1, -100
-	lwi	r25, r1, -96
-	lwi	r24, r1, -92
-	lwi	r23, r1, -88
-	lwi	r22, r1, -84
-	lwi	r21, r1, -80
-	lwi	r20, r1, -76
-	lwi	r19, r1, -72
-	lwi	r18, r1, -68
-	lwi	r17, r1, -64
-	lwi	r16, r1, -60
-	lwi	r15, r1, -56
-	lwi	r14, r1, -52
-	lwi	r13, r1, -48
-	lwi	r12, r1, -44
-	lwi	r11, r1, -40
-	lwi	r10, r1, -36
-	lwi	r9, r1, -32
-	lwi	r8, r1, -28
-	lwi	r7, r1, -24
-	lwi	r6, r1, -20
-	lwi	r5, r1, -16
-	lwi	r4, r1, -12
-	lwi	r3, r1, -8
-	lwi	r2, r1, -4
-
 	rtid	r14, 0
 	nop
 	.size _interrupt_handler,.-_interrupt_handler