ide-cd: unify handling of fs and pc requests in cdrom_decode_status()

Based on earlier work by Borislav Petkov.

Unify handling of fs and pc requests in cdrom_decode_status().

While at it:
- remove unreachable code

The only change in functionality is that for pc requests more
detailed error message will be printed for following sense keys:
* ILLEGAL_REQUEST
* DATA_PROTECT
* MEDIUM_ERROR
* BLANK_CHECK

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>