RISC-V: Enable assert for insn_has_dfa_reservation

Enables assert that every typed instruction is associated with a
dfa reservation

gcc/ChangeLog:

	* config/riscv/riscv.cc (riscv_sched_variable_issue): enable assert

gcc/config/riscv/riscv.cc

@@ -8234,9 +8234,7 @@ riscv_sched_variable_issue (FILE *, int, rtx_insn *insn, int more)
 
   /* If we ever encounter an insn without an insn reservation, trip
      an assert so we can find and fix this problem.  */
-#if 0
   gcc_assert (insn_has_dfa_reservation_p (insn));
-#endif
 
   return more - 1;
 }