BugLink: https://bugs.launchpad.net/bugs/1688132

Rename the [read|write]_sw functions to make it clearer they access
the TWSI registers.
Signed-off-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
(cherry picked from commit 9cb9480e)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Colin King <colin.king@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>