tty: serial: fsl_lpuart: remove sg_set_buf() for sport->rx_sgl

Since .sg_init_one() already set sg entry page like below code.
	sg_init_one()
		sg_init_table(sg, 1);
		sg_set_buf(sg, buf, buflen);

So it should not set sg entry page again, remove the redundant code.

Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Link: https://lore.kernel.org/r/20190717051930.15514-5-fugang.duan@nxp.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>