ata: pata_artop: Repair possible copy/paste issue in 'artop_6210_qc_defer()'s header

Fixes the following W=1 kernel build warning(s):

 drivers/ata/pata_artop.c:278: warning: expecting prototype for artop_6210_qc_defer(). Prototype was for artop6210_qc_defer() instead

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andre Hedrick <andre@linux-ide.org>
Cc: Thibaut VARENE <varenet@parisc-linux.org>
Cc: Alessandro Zummo <alessandro.zummo@towertech.it>
Cc: linux-ide@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>