applesmc: implement error status port

applesmc: implement error status port

As of release 10.12.4, OS X (Sierra) refuses to boot unless the
AppleSMC supports an additional I/O port, expected to provide an
error status code.

Update the [cmd|data]_write() and data_read() methods to implement
the required state machine, and add I/O region & methods to handle
access to the error port.

Originally proposed by Eric Shelton <eshelton@pobox.com> based in
part on FakeSMC (git://git.assembla.com/fakesmc.git).

Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Phil Dennis-Jordan <phil@philjordan.eu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 1497639316-22202-3-git-send-email-gsomlo@gmail.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>