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

 drivers/ata/pata_pdc2027x.c:209: warning: expecting prototype for pdc2027x_pata_cable_detect(). Prototype was for pdc2027x_cable_detect() instead
 drivers/ata/pata_pdc2027x.c:262: warning: expecting prototype for pdc2720x_mode_filter(). Prototype was for pdc2027x_mode_filter() instead
 drivers/ata/pata_pdc2027x.c:513: warning: Function parameter or member 'board_idx' not described in 'pdc_adjust_pll'
 drivers/ata/pata_pdc2027x.c:513: warning: expecting prototype for adjust_pll(). Prototype was for pdc_adjust_pll() instead
 drivers/ata/pata_pdc2027x.c:599: warning: expecting prototype for detect_pll_input_clock(). Prototype was for pdc_detect_pll_input_clock() instead

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Albert Lee <albertcc@tw.ibm.com>
Cc: Andre Hedrick <andre@linux-ide.org>
Cc: Frank Tiernan <frankt@promise.com>
Cc: linux-ide@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>