drivers/input/serio/hp_sdc.c: fix crash when removing hp_sdc module

On parisc machines, which don't have HIL, removing the hp_sdc module
panics the kernel.  Fix this by returning early in hp_sdc_exit() if no HP
SDC controller was found.

Add functionality to probe for the hp_sdc_mlc kernel module (which takes
care of the upper layer HIL functionality on parisc) after two seconds.
This is needed to get all the other HIL drivers (keyboard / mouse/ ..)
drivers automatically loaded by udev later as well.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Frans Pop <elendil@planet.nl>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Grant Grundler <grundler@parisc-linux.org>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>