Input: add option to disable HP SDC driver

Add "no_hpsdc" kernel module option to the hp_sdc driver, so that
the driver can be instructed to not enable the HP SDC port.

This is useful on some older HPPA boxes with HIL keyboard
and HIL mouse where the new HP SDC HIL drivers don't work
yet. By disabling the new hp_sdc driver users are able to use
the older hilkbd driver instead.

Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>