ATR: align get_atr() return value type

type annotations claimed the return type was Hexstr, but in reality
it was a list of integers.  Let's fix that.

Change-Id: I01b247dad40ec986cf199302f8e92d16848bd499
Closes: OS#6322

pySim/transport/pcsc.py

@@ -103,7 +103,7 @@ class PcscSimLink(LinkBaseTpdu):
             raise NoCardError() from exc
 
     def get_atr(self) -> Hexstr:
-        return self._con.getATR()
+        return i2h(self._con.getATR())
 
     def disconnect(self):
         self._con.disconnect()

pySim/transport/serial.py

@@ -21,7 +21,7 @@ import os
 import argparse
 from typing import Optional
 import serial
-from osmocom.utils import h2b, b2h, Hexstr
+from osmocom.utils import h2b, b2h, i2h, Hexstr
 
 from pySim.exceptions import NoCardError, ProtocolError
 from pySim.transport import LinkBaseTpdu
@@ -96,7 +96,7 @@ class SerialSimLink(LinkBaseTpdu):
         self.reset_card()
 
     def get_atr(self) -> Hexstr:
-        return self._atr
+        return i2h(self._atr)
 
     def disconnect(self):
         pass  # Nothing to do really ...