drm/rockchip: inno_hdmi: Remove useless input format

The driver has a lot of logic to deal with multiple input formats, but
hardcodes it to RGB. This means that most of that code has been dead
code, so let's get rid of it.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
Tested-by: Alex Bee <knaerzche@gmail.com>
[made checkpatch happy]
Signed-off-by: Alex Bee <knaerzche@gmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20231222174220.55249-11-knaerzche@gmail.com