gpu: move particle injection back

to before pushing particles. The GPU code is expecting this order,
though it certainly is not desirable to have two different ways of
doing it depending on whether GPU is used or not.

Author: germasch

src/include/psc.hxx

@@ -363,6 +363,15 @@ struct Psc
       prof_stop(pr_collision);
     }
 
+  #ifdef USE_CUDA
+    // === particle injection
+    prof_start(pr_inject_prts);
+    for (auto injector : injectors_) {
+      injector->inject(mprts_, mflds_);
+    }
+    prof_stop(pr_inject_prts);
+#endif
+
     if (checks_.continuity.should_do_check(timestep)) {
       mpi_printf(comm, "***** Checking continuity (1 of 2)...\n");
       prof_start(pr_checks);
@@ -376,12 +385,14 @@ struct Psc
     pushp_.push_mprts(mprts_, mflds_);
     prof_stop(pr_push_prts);
 
+#ifndef USE_CUDA
     // === particle injection
     prof_start(pr_inject_prts);
     for (auto injector : injectors_) {
       injector->inject(mprts_, mflds_);
     }
     prof_stop(pr_inject_prts);
+#endif
 
     // === external current
     prof_start(pr_external_current);