ARM: tegra: remove mach/barriers.h

The barriers implemented in arch/arm/mach-tegra/mach/barriers.h
are exactly the same as the default barriers implemented in
arch/arm/include/asm/system.h.  Remove barriers.h from Tegra,
and don't select ARCH_HAS_BARRIERS.

Signed-off-by: Colin Cross <ccross@android.com>
Acked-by: Olof Johansson <olof@lixom.net>