powerpc: export debug registers save function for KVM

KVM need this function when switching from vcpu to user-space
thread. My subsequent patch will use this function.
Signed-off-by: NBharat Bhushan <bharat.bhushan@freescale.com>
Acked-by: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NScott Wood <scottwood@freescale.com>

arch/powerpc/include/asm/switch_to.h

@@ -35,6 +35,7 @@ extern void giveup_vsx(struct task_struct *);
 extern void enable_kernel_spe(void);
 extern void giveup_spe(struct task_struct *);
 extern void load_up_spe(struct task_struct *);
+extern void switch_booke_debug_regs(struct thread_struct *new_thread);
 
 #ifndef CONFIG_SMP
 extern void discard_lazy_cpu_state(void);

arch/powerpc/kernel/process.c

@@ -371,12 +371,13 @@ static void prime_debug_regs(struct thread_struct *thread)
  * debug registers, set the debug registers from the values
  * stored in the new thread.
  */
-static void switch_booke_debug_regs(struct thread_struct *new_thread)
+void switch_booke_debug_regs(struct thread_struct *new_thread)
 {
 	if ((current->thread.debug.dbcr0 & DBCR0_IDM)
 		|| (new_thread->debug.dbcr0 & DBCR0_IDM))
 			prime_debug_regs(new_thread);
 }
+EXPORT_SYMBOL_GPL(switch_booke_debug_regs);
 #else	/* !CONFIG_PPC_ADV_DEBUG_REGS */
 #ifndef CONFIG_HAVE_HW_BREAKPOINT
 static void set_debug_reg_defaults(struct thread_struct *thread)