[ARM] Restore preempt count before reporting unbalanced preempt count

On ARM, we oops when we detect that an interrupt handler has unbalanced
the preempt count.  We should restore the preempt count when we started
to handle the interrupt and then cause the oops.

arch/arm/kernel/entry-armv.S

@@ -772,8 +772,8 @@ __irq_svc:	sub	sp, sp, #S_FRAME_SIZE
 preempt_return:
 		ldr	r0, [r8, #TI_PREEMPT]		@ read preempt value
 		teq	r0, r7
-		strne	r0, [r0, -r0]			@ bug()
 		str	r9, [r8, #TI_PREEMPT]		@ restore preempt count
+		strne	r0, [r0, -r0]			@ bug()
 #endif
 		ldr	r0, [sp, #S_PSR]		@ irqs are already disabled
 		msr	spsr, r0
@@ -908,8 +908,8 @@ __irq_usr:	sub	sp, sp, #S_FRAME_SIZE
 #ifdef CONFIG_PREEMPT
 		ldr	r0, [r8, #TI_PREEMPT]
 		teq	r0, r7
-		strne	r0, [r0, -r0]
 		str	r9, [r8, #TI_PREEMPT]
+		strne	r0, [r0, -r0]
 		mov	tsk, r8
 #else
 		get_thread_info tsk