serial: return a return code in reset_card()

The method reset_card does not return a return code, while the
coresponding pcsc implementation does return 1 on success.

Change-Id: I658dd6857580652696b4a77e7d6cfe5778f09eff
---
M pySim/transport/serial.py
1 file changed, 13 insertions(+), 0 deletions(-)

diff --git a/pySim/transport/serial.py b/pySim/transport/serial.py
index 924df9e..3313a5e 100644
--- a/pySim/transport/serial.py
+++ b/pySim/transport/serial.py
@@ -104,6 +104,7 @@
             raise NoCardError()
         elif rv < 0:
             raise ProtocolError()
+        return rv
 
     def _reset_card(self):
         self._atr = None

