powerpc/idle/6xx: Use r1 with CURRENT_THREAD_INFO()

Make sure CURRENT_THREAD_INFO() is used with r1 which is the virtual
address of the stack, in order to ease the switch to r2 when we enable
THREAD_INFO_IN_TASK, as we have no register having the phys address of
current.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
[mpe: Split out of larger patch]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/idle_6xx.S

@@ -159,7 +159,8 @@ _GLOBAL(power_save_ppc32_restore)
 	stw	r9,_NIP(r11)		/* make it do a blr */
 
 #ifdef CONFIG_SMP
-	CURRENT_THREAD_INFO(r12, r11)
+	CURRENT_THREAD_INFO(r12, r1)
+	tophys(r12, r12)
 	lwz	r11,TI_CPU(r12)		/* get cpu number * 4 */
 	slwi	r11,r11,2
 #else