checkpatch: forbid implied-barrier I/O functions.

Forbid read[bwl], write[bwl], in[bwl], and out[bwl], as they
contain a 'stealth barrier' which can harm performance.
Developers are expected to call appropriate __raw_* or *_relaxed
APIs and manage barriers explicitly.

Change-Id: Ie4da221c91a0505917199db9e2fdb704c3e47d44
Signed-off-by: Gregory Bean <gbean@codeaurora.org>
(cherry picked from commit 032fd4ba09e195d9913c08f460130da9905936ef)
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>