disas: Make disassemble_info::target_info field const

Disassemblers shouldn't need writeable context, so make the
disassemble_info::target_info field const.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20260202222412.24923-7-philmd@linaro.org>

include/disas/dis-asm.h

@@ -397,7 +397,7 @@ typedef struct disassemble_info {
   bool show_opcodes;
 
   /* Field intended to be used by targets in any way they deem suitable.  */
-  void *target_info;
+  const void *target_info;
 
   /* Options for Capstone disassembly.  */
   int cap_arch;