arch,cris: Convert smp_mb__*()

Cris fully relies on asm-generic/barrier.h, therefore its smp_mb() is
barrier(), thus we can use the default implementation that uses
smp_mb().

(Include asm/system.h and asm/barrier.h to avoid header dependency hell.)

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/n/tip-wvewbe8os3s1e4pt1cdotuee@git.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mikael Starvik <starvik@axis.com>
Cc: linux-cris-kernel@axis.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>