tests/drivers display_read_write: Move common kconfig option to overlay

For native_sim[//64], these tests need to be built with
CONFIG_SDL_DISPLAY_USE_HARDWARE_ACCELERATOR=n

Until now we defined this option in the yaml file for each test
targetting the sdl display driver.
But if somebody builds the test directly, it will fail as these yaml
kconfig defined options would not be used.

Let's instead define it in a board overlay, so in that case the test
will also work.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>