riscv: remove unused barrier defines
They were introduced in commit fab957c11efe ("RISC-V: Atomic and
Locking Code") long after commit 2e39465abc4b ("locking: Remove
deprecated smp_mb__() barriers") removed the remnants of all previous
instances from the tree.
Signed-off-by: Rolf Eike Beer <eb at emlix.com>
[paul.walmsley at sifive.com: stripped spurious mbox header from patch
description; fixed commit references in patch header]
Signed-off-by: Paul Walmsley <paul.walmsley at sifive.com>UnifiedSplitRaw
