drm/rockchip: inno_hdmi: Remove unneeded has audio flag

The sink_has_audio flag is not used anywhere in the driver so let's get
rid of it. It's redundant with drm_display_info.has_audio anyway.

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/20231222174220.55249-10-knaerzche@gmail.com