drm/rockchip: Implement CRC debugfs API

drm/rockchip: Implement CRC debugfs API

Implement the .set_crc_source() callback and call the DP helpers
accordingly to start and stop CRC capture.

This is only done if this CRTC is currently using the eDP connector.

v3: Remove superfluous check on rockchip_crtc_state->output_type

v6: Remove superfluous variable

Signed-off-by: Tomeu Vizoso <[email protected]>
Acked-by: Mark Yao <[email protected]>
Signed-off-by: Sean Paul <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]