[PCMCIA] card insert / eject

[PCMCIA] card insert / eject

Patch from Dominik Brodowski

Add two further attributes, "card_insert" and "card_eject". Reading
these files will fail; but writing _anything_ non-empty to these
files will execute an user insert/ejection request -- equivalent
to "cardctl insert", "cardctl eject".

To ensure proper error values to userspace, transform the return
values from CS_ error codes to -E error codes.