Input: cros_ec_keyb - switch to using generic device properties

In preparation to enabling this driver on x86 devices let's switch
from OF-specific property API to the generic one.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20220526231230.2805147-1-dmitry.torokhov@gmail.com


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