Input: i8042 - add PNP modaliases

This allows the module to be autoloaded in the common case.

In order to work on non-PnP systems the module should be compiled in or
loaded unconditionally at boot (c.f. modules-load.d(5)), as before.

Signed-off-by: Tom Gundersen <teg@jklm.no>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>