ide-cd: convert driver to new ide debugging macro (v3)

Also,

- leave in the possibility for optimizing away all debugging macros
- add a PFX macro and prepend all printk calls with it for consistency
- add debug macro calls in important driver paths
- remove #if 0-ed code
- mv restore_request -> ide_cd_restore_request
- add a driver registration printk

v2:
failed_command can be NULL so check it before accessing it

v3:
fix another NULL ptr in debug statement

There should be no functionality change resulting from this patch.
Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>