Input: matrix_keypad - allow platform to disable key autorepeat

In an embedded system the matrix_keypad driver might be used to
interface with an external control panel and not an actual keyboard.
On the control panel some of the keys could be used to turn on/off
various functions.  If key autorepeat is enabled this causes the
function to quickly toggle between the on and off states and makes
operation difficult.

Add an option in the platform-specific data to disable the key
autorepeat.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>