rt2x00: Synchronize WCID initialization with legacy driver

Legacy rt2870 driver handles WCID differently then we expected,
the BSSID and Cipher value are 3 bit values, while the 4th bit
should be set elsewhere in an extended field.

After this, rt2800usb reports frames have been decrypted
successfully, indicating that the Hardware decryption now is
working correctly.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>