powerpc: Fix for getting CPU number in power_save_ppc32_restore()

The calculation to get TI_CPU based off of SPRG3 was just plain wrong,
meaning that we were getting garbage for the CPU number on 6xx/G3/G4
based SMP boxes in this code.

Just offset off the stack pointer (to get to thread_info) like all the
other references to TI_CPU do.

This was pointed out by Chen Gong <G.Chen@freescale.com>

[paulus@samba.org - use rlwinm r12,r11,... instead of
 rlwinm r12,r1,...; tophys()]
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/idle_6xx.S

@@ -158,7 +158,7 @@ _GLOBAL(power_save_ppc32_restore)
 	stw	r9,_NIP(r11)		/* make it do a blr */
 
 #ifdef CONFIG_SMP
-	mfspr	r12,SPRN_SPRG3
+	rlwinm	r12,r11,0,0,31-THREAD_SHIFT
 	lwz	r11,TI_CPU(r12)		/* get cpu number * 4 */
 	slwi	r11,r11,2
 #else

arch/powerpc/kernel/idle_e500.S

@@ -84,10 +84,11 @@ _GLOBAL(power_save_ppc32_restore)
 	stw	r9,_NIP(r11)		/* make it do a blr */
 
 #ifdef CONFIG_SMP
-	mfspr	r12,SPRN_SPRG3
+	rlwinm	r12,r1,0,0,31-THREAD_SHIFT
 	lwz	r11,TI_CPU(r12)		/* get cpu number * 4 */
 	slwi	r11,r11,2
 #else
 	li	r11,0
 #endif
+
 	b	transfer_to_handler_cont