Revert "rx: fix rx_atomic warnings under Solaris"

Revert "rx: fix rx_atomic warnings under Solaris"

This reverts commit ae4ad509d35aab73936a1999410bd80bcd711393. While
that commit did fix the mentioned warnings on Solaris, it also changed
the size of rx_atomic_t. Our code in rx_stats.c assumes that an
rx_atomic_t is 4-bytes wide, and so changing the size of rx_atomic_t
broke our reporting for stats in the 'rx_stats' structure.

To fix this, revert that commit. This reintroduces the mentioned
warnings, but those warnings are reported for our atomic bit-op
functions, which are unused and will be removed by another commit.

Change-Id: Ie3e72cc06690d9f8de79e8f0274ea51079004c38
Reviewed-on: https://gerrit.openafs.org/13415
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>