powerpc: Clear HID0 attention enable on PPC970 at boot time (CVE-2006-4093)

Clear HID0[en_attn] at CPU init time on PPC970.  Closes CVE-2006-4093.
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

arch/powerpc/kernel/cpu_setup_power4.S

@@ -94,6 +94,8 @@ _GLOBAL(__setup_cpu_ppc970)
 	mfspr	r0,SPRN_HID0
 	li	r11,5			/* clear DOZE and SLEEP */
 	rldimi	r0,r11,52,8		/* set NAP and DPM */
+	li	r11,0
+	rldimi	r0,r11,32,31		/* clear EN_ATTN */
 	mtspr	SPRN_HID0,r0
 	mfspr	r0,SPRN_HID0
 	mfspr	r0,SPRN_HID0