sony-laptop: support new hotkeys on the P, Z and EC series

Add new mappings for assist, VAIO, zoom and eject buttons present on
refurbished P, Z and EC models.

Reported-by: Gyorgy Jeney <nog.lkml@gmail.com>
Reported-by: Stephan Mueller <smueller@chronox.de>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Matthew Garrett <mjg@redhat.com>