target/xtensa: disas/xtensa: fix coverity warnings

Coverity warnings CID 1385146, 1385148 1385149 and 1385150 point that
xtensa_opcode_num_operands and xtensa_format_num_slots may return -1
even when xtensa_opcode_decode and xtensa_format_decode succeed. In that
case unsigned counters used to iterate through operands/slots will not
do the right thing.
Make counters and loop bounds signed to fix the warnings.
Signed-off-by: NMax Filippov <jcmvbkbc@gmail.com>

disas/xtensa.c

@@ -37,7 +37,7 @@ int print_insn_xtensa(bfd_vma memaddr, struct disassemble_info *info)
     bfd_byte *buffer = g_malloc(1);
     int status = info->read_memory_func(memaddr, buffer, 1, info);
     xtensa_format fmt;
-    unsigned slot, slots;
+    int slot, slots;
     unsigned len;
 
     if (status) {
@@ -79,7 +79,7 @@ int print_insn_xtensa(bfd_vma memaddr, struct disassemble_info *info)
 
     for (slot = 0; slot < slots; ++slot) {
         xtensa_opcode opc;
-        unsigned opnd, vopnd, opnds;
+        int opnd, vopnd, opnds;
 
         if (slot) {
             info->fprintf_func(info->stream, "; ");

target/xtensa/translate.c

@@ -942,7 +942,7 @@ static void disas_xtensa_insn(CPUXtensaState *env, DisasContext *dc)
     unsigned char b[MAX_INSN_LENGTH] = {cpu_ldub_code(env, dc->pc)};
     unsigned len = xtensa_op0_insn_len(dc, b[0]);
     xtensa_format fmt;
-    unsigned slot, slots;
+    int slot, slots;
     unsigned i;
 
     if (len == XTENSA_UNDEFINED) {
@@ -969,7 +969,7 @@ static void disas_xtensa_insn(CPUXtensaState *env, DisasContext *dc)
     slots = xtensa_format_num_slots(isa, fmt);
     for (slot = 0; slot < slots; ++slot) {
         xtensa_opcode opc;
-        unsigned opnd, vopnd, opnds;
+        int opnd, vopnd, opnds;
         uint32_t raw_arg[MAX_OPCODE_ARGS];
         uint32_t arg[MAX_OPCODE_ARGS];
         XtensaOpcodeOps *ops;