Move functions to group them logically. Device and I2C functions go in separate
places. No functional changes (really!).

Signed-off-by: Juerg Haefliger <juergh at gmail.com>
Acked-by: NJean Delvare <khali@linux-fr.org>
Signed-off-by: NMark M. Hoffman <mhoffman@lightlink.com>