This defines __smp_xxx barriers for xtensa,
for use by virtualization.

smp_xxx barriers are removed as they are
defined correctly by asm-generic/barriers.h
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NPeter Zijlstra (Intel) <peterz@infradead.org>