powerpc: Initialize LPCR:DPFD on power7 to a sane default

This sets the default data stream prefetch size for operating
systems that don't set their own value in DSCR. We use 4 which
is "medium".
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/cpu_setup_power7.S

@@ -54,6 +54,7 @@ __init_LPCR:
 	 *
 	 *   LPES = 0b01 (HSRR0/1 used for 0x500)
 	 *   PECE = 0b111
+	 *   DPFD = 4
 	 *
 	 * Other bits untouched for now
 	 */
@@ -61,6 +62,12 @@ __init_LPCR:
 	ori	r3,r3,(LPCR_LPES0|LPCR_LPES1)
 	xori	r3,r3, LPCR_LPES0
 	ori	r3,r3,(LPCR_PECE0|LPCR_PECE1|LPCR_PECE2)
+	li	r5,7
+	sldi	r5,r5,LPCR_DPFD_SH
+	andc	r3,r3,r5
+	li	r5,4
+	sldi	r5,r5,LPCR_DPFD_SH
+	or	r3,r3,r5
 	mtspr	SPRN_LPCR,r3
 	isync
 	blr