net/wan/fsl_ucc_hdlc: GUMR for non tsa mode

The following bits in the GUMR is changed for non
tsa mode: CDS, CTSP and CTSS are set to zero.

When set, there is no tx interrupts from the controller.

Signed-off-by: David Gounaris <david.gounaris@infinera.com>
Signed-off-by: David S. Miller <davem@davemloft.net>