fsl_i2c: Do not generate STOP after read.

__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: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>