Input: psmouse - move protocol descriptions around

We move protocol descriptions and psmouse_find_by_type() and
pmouse_find_by_name() so that we can use them without forward declarations
in the subsequent patches.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Tested-by: Marcin Sochacki <msochacki+kernel@gmail.com>
Tested-by: Till <till2.schaefer@uni-dortmund.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>