Input: ibmasm - convert to dynamic input_dev allocation

Update the ibmasm driver to use the dynamic allocation of input_dev
structs to work with the sysfs subsystem.

Vojtech: Fixed some problems/bugs in the patch.
Dmitry: Fixed some more.

Signed-off-by: Vernon Mauery <vernux@us.ibm.com>
Signed-off-by: Vojtech Pavlik <vojtech@suse.cz>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>