ARM: 8582/1: remove unused CONFIG_ARCH_HAS_BARRIERS

Since commit 2b749cb3 ("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>