WIP: DT-bindings: asus-tf300t: let bootloader setup memory timings

- fixes flickering display on Jasper device

Suggested-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Jasper Korten <jja2000@gmail.com>
Signed-off-by: David Heidelberg <david@ixit.cz>

Author: okias