eeepc-laptop: refactor notifications

Separate out input_notify(), in a similar way to how notify_brn()
is already separated.  This will allow all the functions which refer to
the input device to be grouped together.

This includes a small behaviour change - we now synthesize brightness
up/down key events even if the brightness is already at the
maximum/minimum value.  This is consistent with the new uevent
interface.

Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Signed-off-by: Len Brown <len.brown@intel.com>