Input: remove use of __devexit_p

CONFIG_HOTPLUG is going away as an option so __devexit_p is no longer
needed.

Signed-off-by: Bill Pemberton <wfp5p@virginia.edu>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>