amilo-rfkill: Add dependency on SERIO_I8042

I forgot to add this when changing the driver to use the proper
i8042 functions.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>