scd: Fix ccid-driver timeout for OpenPGPcard v2.1.
* scd/ccid-driver.c (CCID_CMD_TIMEOUT): New. (ccid_transceive_apdu_level, ccid_transceive): Use.
It is reported that key generation causes timeout with OpenPGPcard
v2.1. Ideally, timeout value could be determined at run-time by
examining card's ATR. Compile-time fixed value is OK for internal
CCID driver.