Multi_ReadProc() exits on the *last* slot exit
Multi_ReadProc() exits on the *last* slot exit

The function to read data from multi-slots readers should exit only when
the last slot is terminated.

Before the change, the function was terminated with the _first_ slot. So
it was not possible to send PowerDown commands to the other slots of the
same reader.

LudovicRousseau/CCID,LudovicRousseau/CCID,LudovicRousseau/CCID