Cast up `int` instruction code to `VALUE`

Fix Visual C warnings:
```
iseq.c(3793): warning C4312: 'type cast': conversion from 'int' to 'void *' of greater size
iseq.c(3794): warning C4312: 'type cast': conversion from 'int' to 'void *' of greater size
```

1 files changed, 1 insertions, 1 deletions

diff --git a/iseq.c b/iseq.c
index 528c0acef9..d17ce486c5 100644
--- a/iseq.c
+++ b/iseq.c
@@ -3390,7 +3390,7 @@ rb_vm_encoded_insn_data_table_init(void)
     const void * const *table = rb_vm_get_insns_address_table();
 #define INSN_CODE(insn) ((VALUE)table[insn])
 #else
-#define INSN_CODE(insn) (insn)
+#define INSN_CODE(insn) ((VALUE)(insn))
 #endif
     st_data_t insn;
     encoded_insn_data = st_init_numtable_with_size(VM_INSTRUCTION_SIZE / 2);