smartcard: Don't list two readers when there's only ne

$ opensc-tool -l
# Detected readers (pcsc)
Nr.  Card  Features  Name
0    Yes             L5 built-in SmartCard Reader 00 01 00 00
1    Yes             L5 built-in SmartCard Reader 00 01 00 01

Similar things happen with pcsc_scan. We can limit slots in config but I have no idea yet what the right fix for the problem is.