drm/rockchip: inno_hdmi: Remove useless copy of drm_display_mode

The driver maintains a copy of the adjusted mode but doesn't use it
anywhere. Remove it.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
Tested-by: Alex Bee <knaerzche@gmail.com>
Signed-off-by: Alex Bee <knaerzche@gmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20231222174220.55249-6-knaerzche@gmail.com