sc1200: remove redundant warning message from sc1200_tune_chipset()

ide_config_drive_speed() called by sc1200_set_xfer_mode() already gives
a meaningful warning message in case of failure.

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>