ide-cd: unify cdrom_newpc_intr() exit paths

* Move cdrom_end_request() calls from cdrom_decode_status()
  and ide_cd_check_ireason() to cdrom_newpc_intr().

* Unify cdrom_newpc_intr() exit paths.

There should be no functional changes caused by this patch.

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