rtc_cmos: convert shutdown to new pnp_driver->shutdown

commit abd6633c

 ("pnp: add a shutdown
method to pnp drivers") adds shutdown method to bus driver blindly.  With
it, driver->shutdown is no longer valid.

Use pnp_driver->shutdown instead.

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=14889

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Reported-by: Malte Schröder <maltesch@gmx.de>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: David Hardeman <david@hardeman.nu>
Cc: Dmitry Torokhov <dtor@mail.ru>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Paul Gortmaker <p_gortmaker@yahoo.com>
Cc: <stable@kernel.org>		[2.6.32.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>