Input: synaptics - add another Protege M300 to rate blacklist

Apparently some of Toshiba Protege M300 identify themselves as
"Portable PC" in DMI so we need to add that to the DMI table as
well. We need DMI data so we can automatically lower Synaptics
reporting rate from 80 to 40 pps to avoid over-taxing their
keyboard controllers.

Tested-by: Rod Davison <roddavison@gmail.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>