RISC-V: Fix CSR hashtable initialization

This commit fixes the issue which repeatedly initializing CSR hashtable
everytime we parse an CSR and makes sure that CSR hashtable initialization
occurs when either architecture or option is changed (e.g. setting a
disassembler option `priv-spec' on GDB may change the privileged spec
version, changing canonical CSR names dynamically).

opcodes/ChangeLog:

	* riscv-dis.c (init_dis_per_arch_and_options): Reset the CSR
	init flag for privileged spec version change.
	(print_insn_args): Don't repeatedly initialize CSR hashtable.
	Use a file scope flag to initialize CSR hashtable to enable
	resetting the flag.

opcodes/riscv-dis.c

@@ -68,6 +68,10 @@ static bool no_aliases = false;
 /* If set, disassemble with numeric registers.  */
 static bool is_numeric = false;
 
+/* Reset when either arch or option is changed.  */
+static bool is_init_csr = false;
+
+
 static void
 set_default_riscv_dis_options (void)
 {
@@ -178,6 +182,8 @@ init_dis_per_arch_and_options (void)
   /* If arch has Zfinx extension, use GPR to disassemble.  */
   if (riscv_subset_supports (&riscv_rps_dis, "zfinx"))
     riscv_fpr_names = riscv_gpr_names;
+  /* Reset CSR hashtable because `priv-spec' option may change the names.  */
+  is_init_csr = false;
 }
 
 /* Print one argument from an array.  */
@@ -534,10 +540,9 @@ print_insn_args (const char *oparg, insn_t l, bfd_vma pc, disassemble_info *info
 	case 'E':
 	  {
 	    static const char *riscv_csr_hash[4096]; /* Total 2^12 CSRs.  */
-	    static bool init_csr = false;
 	    unsigned int csr = EXTRACT_OPERAND (CSR, l);
 
-	    if (!init_csr)
+	    if (!is_init_csr)
 	      {
 		unsigned int i;
 		for (i = 0; i < 4096; i++)
@@ -558,6 +563,7 @@ print_insn_args (const char *oparg, insn_t l, bfd_vma pc, disassemble_info *info
 		DECLARE_CSR (name, num, class, define_version, abort_version)
 #include "opcode/riscv-opc.h"
 #undef DECLARE_CSR
+		is_init_csr = true;
 	      }
 
 	    if (riscv_csr_hash[csr] != NULL)