dt-bindings: input: matrix_keypad: add settle time after enabling all columns

Matrix keypads with high capacity need a longer settle time after
enabling all columns. Add an optional property to specify the settle
time.

Signed-off-by: Markus Burri <markus.burri@mt.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Manuel Traut <manuel.traut@mt.com>
Link: https://lore.kernel.org/r/20250110054906.354296-6-markus.burri@mt.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>