sw_inj_frames.c: a couple of minor fixes so that this compiles
The code used for generating the S6 CW software injections (sw_inj_frames.c) no longer compiles (although it is not in the lalsuite build). This PR fixes the two bugs that prevented compilation in case anyone wants to make use of it in the future. The channel names used in the code are still hardcoded, so future users (if there are any) may want to change this.