Perform I2C transmission in a single burst when mode is "none" or not set

Some more automated I2C controllers cannot explicitly create
START/STOP/etc. conditions on the bus.
Instead, the correct condition is set automatically according
to the pending transfer status.
This particular behavior can cause trouble if some I2C slave
requires sending address offset within the chip followed by
the actual data or command. In that case we cannot assume that
the driver will not STOP immediately after sending
offset.

To avoid that, do not split offset transfer from data transfer
for default transmission modes and do exactly that if requested
in command line (stop-start and repeated-start modes).
This more generic approach should cover special cases like
the one described.

Reviewed by: imp
Submitted by: Marcin Mazurek <mma@semihalf.com>
Obtained from: Semihalf