fec,pbch: remove unused variables

unused code that moreover was causing TSAN to complain, e.g.
in the ue_phy_test

lib/src/phy/fec/convolutional/viterbi37_avx2_16bit.c

@@ -43,7 +43,6 @@ union branchtab27 {
 
 } Branchtab37_sse2[3];
 
-int firstGo_16bit;
 /* State info for instance of Viterbi decoder */
 struct v37 {
   metric_t    metrics1;                  /* path metric buffer 1 */
@@ -85,7 +84,6 @@ int init_viterbi37_avx2_16bit(void* p, int starting_state)
     vp->metrics1.c[i] = 63;
 
   clear_v37_avx2_16bit(vp);
-  firstGo_16bit   = 1;
   vp->old_metrics = &vp->metrics1;
   vp->new_metrics = &vp->metrics2;
   vp->dp          = vp->decisions;

lib/src/phy/phch/pbch.c

@@ -40,15 +40,11 @@ bool srsran_pbch_exists(int nframe, int nslot)
   return (!(nframe % 5) && nslot == 1);
 }
 
-cf_t* offset_original;
-
 int srsran_pbch_cp(cf_t* input, cf_t* output, srsran_cell_t cell, bool put)
 {
   int   i;
   cf_t* ptr;
 
-  offset_original = input;
-
   if (put) {
     ptr = input;
     output += cell.nof_prb * SRSRAN_NRE / 2 - 36;