__i2c_read always ends with a STOP condition thereby releasing
the bus. It is cleaner to do the STOP magic in i2c_read(), like
i2c_write() does. This may also help future multimaster systems which
wants to hold on to the bus until all transactions are finished.
Signed-off-by: NJoakim Tjernlund <Joakim.Tjernlund@transmode.se>