i2c: mvtwsi: Handle zero-length offsets properly

i2c: mvtwsi: Handle zero-length offsets properly

Zero-length offsets are not properly handled by the driver. When a read
operation with a zero-length offset is started, a START condition is
asserted, and since no offset bytes are transferred, a repeated START is
issued immediately after, which confuses the controller.

To fix this, we send the first START only if any address bytes need to
be sent, and keep track of the expected start status accordingly.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Reviewed-by: Stefan Roese <sr@denx.de>