MIPS: Remove unused macros from barrier.h

The smp_llsc_rmb() and smp_llsc_wmb() macros are not used in the tree,
remove them.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/848/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>