[ARM SMP] Ensure secondary CPUs see their pen release

Since the secondary CPUs will not be operating in symetric mode
while they are held in the pen, we need to ensure that the write
to pen_release is visible to them, by flushing the cache.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-integrator/platsmp.c

@@ -15,6 +15,7 @@
 #include <linux/mm.h>
 
 #include <asm/atomic.h>
+#include <asm/cacheflush.h>
 #include <asm/delay.h>
 #include <asm/mmu_context.h>
 #include <asm/procinfo.h>
@@ -80,6 +81,7 @@ int __cpuinit boot_secondary(unsigned int cpu, struct task_struct *idle)
 	 * "cpu" is Linux's internal ID.
 	 */
 	pen_release = cpu;
+	flush_cache_all();
 
 	/*
 	 * XXX