[SERIAL] serial8250: convert to the new platform device interface

Do not use platform_device_register_simple() as it is going away.
Also set up driver's owner to create link driver->module in sysfs.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>