ARM: add soc memory barrier extension

Add an extension to the heavy barrier code to allow a SoC specific
memory barrier function to be provided.  This is needed for platforms
where the interconnect has weak ordering, and thus needs assistance
to ensure that memory writes are properly visible in the correct order
to other parts of the system.

Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Richard Woodruff <r-woodruff2@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/flush.c

@@ -22,12 +22,16 @@
 #include "mm.h"
 
 #ifdef CONFIG_ARM_HEAVY_MB
+void (*soc_mb)(void);
+
 void arm_heavy_mb(void)
 {
 #ifdef CONFIG_OUTER_CACHE_SYNC
 	if (outer_cache.sync)
 		outer_cache.sync();
 #endif
+	if (soc_mb)
+		soc_mb();
 }
 EXPORT_SYMBOL(arm_heavy_mb);
 #endif