sim: riscv: Fix build issue due to recent binutils commit

The commit c144f63833 removed INSN_CLASS_A and
added INSN_CLASS_ZAAMO and INSN_CLASS_ZALRSC instead,
which broke the build of the sim for riscv targets.

Fix that by using the new INSN_CLASS types.

Fixes: c144f63833 ("RISC-V: Support B, Zaamo and Zalrsc extensions.")

Approved-By: Tom Tromey <tom@tromey.com>

sim/riscv/sim-main.c

@@ -1299,7 +1299,8 @@ execute_one (SIM_CPU *cpu, unsigned_word iw, const struct riscv_opcode *op)
 
   switch (op->insn_class)
     {
-    case INSN_CLASS_A:
+    case INSN_CLASS_ZAAMO:
+    case INSN_CLASS_ZALRSC:
       return execute_a (cpu, iw, op);
     case INSN_CLASS_C:
       /* Check whether model with C extension is selected.  */