fix length of frame generated by f_TC_rll_ud_ind

Because trxcon now requires frames of a minimum size some
BTS tests which send unpadded frames with a short payload
have started to fail.

Extend the payload size generated by f_TC_rll_ud_ind()
to make TC_rll_unit_data_ind_DCCH pass again.

Change-Id: Ibaa4124ebdec96623f48c38fac702e9bbd843869
Related: OS#3415
1 file changed