i2c: omap: Move the remove constraint

Currently we just queue the transfer and release the
qos constraints, however we do not wait for the transfer
to complete to release the constraint. Move the remove
constraint after the bus busy as we are sure that the
transfers are completed by then.

Acked-by: Jean Pihet <j-pihet@ti.com>
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>