compiler warning fixes in PWGDIL

compiler warning fixes in PWGDIL. They appear on Mac compilations during CI tests.

analysis/PWGDIL/dielectron/conversion/CbmAnaConversion.cxx
[CTest: warning matched] /Users/fairroot/builds/computing/cbmroot/analysis/PWGDIL/dielectron/conversion/CbmAnaConversion.cxx:1474:35: warning: overlapping comparisons always evaluate to true [-Wtautological-overlap-compare]
          if (grandmotherId != -1 || grandmotherId == -1) {
[CTest: warning suppressed]               ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
[CTest: warning matched] /Users/fairroot/builds/computing/cbmroot/analysis/PWGDIL/dielectron/conversion/CbmAnaConversion.cxx:1468:26: warning: overlapping comparisons always evaluate to true [-Wtautological-overlap-compare]
      if (motherId != -1 || motherId == -1) {
[CTest: warning suppressed]           ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
[CTest: warning suppressed] 2 warnings generated.

analysis/PWGDIL/dielectron/conversion/CbmAnaConversion.cxx

@@ -1465,13 +1465,13 @@ void CbmAnaConversion::FillMCTracklists(CbmMCTrack* mctrack, int)
     mctrack->GetStartVertex(v);
     if (v.Z() <= 70) {
       int motherId = mctrack->GetMotherId();
-      if (motherId != -1 || motherId == -1) {
+      if (motherId >= 0) {
         CbmMCTrack* mother = (CbmMCTrack*) fMcTracks->At(motherId);
         int mcMotherPdg    = -1;
         if (NULL != mother) mcMotherPdg = mother->GetPdgCode();
         if (mcMotherPdg == 22 || mcMotherPdg == 111 || mcMotherPdg == 221) {
           int grandmotherId = mother->GetMotherId();
-          if (grandmotherId != -1 || grandmotherId == -1) {
+          if (grandmotherId >= 0 || true) {
             //	CbmMCTrack* grandmother = (CbmMCTrack*) fMcTracks->At(grandmotherId);
             //	int mcGrandmotherPdg = -1;
             //	if (NULL != grandmother) mcGrandmotherPdg = grandmother->GetPdgCode();