Restore the OMAP4 barrier behaviour using the new implementation which
allows multiplatform systems to hook into the mb() and wmb() ARM
implementations to perform any necessary additional barrier maintanence.

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>