ppc64: add missing memory barriers in cpu bringup code,

from Colin Devilbiss

arch/ppc64/kernel/smp.c

@@ -171,6 +171,13 @@ static void smp_iSeries_kick_cpu(int nr)
 	lpPaca = paca[nr].xLpPacaPtr;
 	if ( lpPaca->xDynProcStatus >= 2 )
 		return;
+
+	/* The information for processor bringup must
+	 * be written out to main store before we release
+	 * the processor.
+	 */
+	mb();
+
 	/* The processor is currently spinning, waiting
 	 * for the xProcStart field to become non-zero
 	 * After we set xProcStart, the processor will
@@ -236,6 +243,12 @@ smp_kick_cpu(int nr)
 	     ( nr >= MAX_PACAS ) )
 		return;
 
+	/* The information for processor bringup must
+	 * be written out to main store before we release
+	 * the processor.
+	 */
+	mb();
+
 	/* The processor is currently spinning, waiting
 	 * for the xProcStart field to become non-zero
 	 * After we set xProcStart, the processor will