use is_thumb instead

Author: ucgJhe

qiling/debugger/qdb/arch/arch_arm.py

@@ -67,7 +67,8 @@ def thumb_mode(self) -> bool:
         helper function for checking thumb mode
         """
 
-        return self.ql.arch.regs.cpsr & 0x00000020 != 0
+        return self.ql.arch.is_thumb
+
 
     def read_insn(self, address: int) -> bytes:
         """