drm/bridge: lt9611: Fix handling of 4k panels

drm/bridge: lt9611: Fix handling of 4k panels

commit d1a97648ae028a44536927c87837c45ada7141c9 upstream.

4k requires two dsi pipes, so don't report MODE_OK when only a
single pipe is configured. But rather report MODE_PANEL to
signal that requirements of the panel are not being met.

Reported-by: Peter Collingbourne <pcc@google.com>
Suggested-by: Peter Collingbourne <pcc@google.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Tested-by: Anibal Limon <anibal.limon@linaro.org>
Tested-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Vinod Koul <vkoul@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201217140933.1133969-1-robert.foss@linaro.org
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>