qd65xx: return error value in qd_probe()

Return error value in qd_probe() and use it in qd65xx_init()
instead of checking ide_hwifs[].chipset.

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