Clean up some ARMv4/ARMv5 cruft.

Change-Id: I29e836fea4b53901e29f96c6888869c35f6726be
Clean up the pthread-only atomic stuff a little.

It looks like we can probably just use the generic GCC stuff instead;
the generated code looks pretty similar. We should come back to that.

These routines are only used by the pthread implementation, and
__bionic_atomic_inc isn't used, so we can remove it.

Change-Id: I8b5b8cb30a1b159f0e85c3675aee06ddef39b429
ARM: Change dmb domain for bionic_atomic_barrier()

This patch changes the domain that the memory barrier operates on. Assumes
that the scope of bionic_atomic_barrier() does not include device memory,
memory shared with the GPU or any other memory external to the processor
cluster.

Change-Id: I291e741c98a64c86f3a3cf99811bbf1e714ac9aa
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>