dt-bindings: display: sitronix, st7735r: Remove spi-max-frequency limit

dt-bindings: display: sitronix, st7735r: Remove spi-max-frequency limit

The datasheet lists the minimum Serial clock cycle (Write) as 66ns which is
15MHz. Mostly it can do much better than that and is in fact often run at
32MHz. With a clever driver that runs configuration commands at a low speed
and only the pixel data at the maximum speed the configuration can't be
messed up by transfer errors and the speed is only limited by the amount of
pixel glitches that one is able to tolerate.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: David Lechner <david@lechnology.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211124150757.17929-4-noralf@tronnes.org