Includes a function to set TS MODE property os si2168. The function
either disables the TS output bus, or sets mode to config option.

When going to sleep the TS bus is turned off, this makes the driver
compatible with multiple frontend usage.
Signed-off-by: Brad Love <brad@nextdimension.cc>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>