ARM: 8582/1: remove unused CONFIG_ARCH_HAS_BARRIERS

Since commit 2b749cb3a5 ("ARM: realview: remove private barrier
implementation"), this config is not used by any platform.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/Kconfig

@@ -1025,12 +1025,6 @@ config ARM_DMA_MEM_BUFFERABLE
 
 	  You are recommended say 'Y' here and debug any affected drivers.
 
-config ARCH_HAS_BARRIERS
-	bool
-	help
-	  This option allows the use of custom mandatory barriers
-	  included via the mach/barriers.h file.
-
 config ARM_HEAVY_MB
 	bool