cosa: Convert from class_device to device for cosa sync driver

struct class_device is going away, this converts the code to use struct
device instead.

Signed-off-by: Tony Jones <tonyj@suse.de>
Cc: Jan "Yenya" Kasprzak <kas@fi.muni.cz>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>