sim: cgen: inline cgen_init logic

This function has done only one thing: post-process command line
settings to see if profiling or tracing has been enabled, and if
so, set the run_fast_p flag in the simulator state.  That flag is
only used in one place: to select the fast or slow cgen engine.
By inlining the run_fast_p logic to the one place it's used, we
can delete a good amount of logic specific to cgen ports: both
the call to cgen_init and the conditional simulator state.  This
in turn allows us to have a single simulator state struct across
all ports so we can share objects more between them, and makes
the sim_open calls look more consistent.

sim/bpf/sim-if.c

@@ -175,10 +175,6 @@ sim_open (SIM_OPEN_KIND kind,
     bpf_cgen_init_dis (cd);
   }
 
-  /* Initialize various cgen things not done by common framework.
-     Must be done after bpf_cgen_cpu_open.  */
-  cgen_init (sd);
-
   /* XXX do eBPF sim specific initializations.  */
 
   return sd;