drm/dp: WARN about invalid/unknown link rates and bw codes

drm/dp: WARN about invalid/unknown link rates and bw codes

Falling back to the lowest value is likely the only thing we can do, but
doing it silently seems like a bad thing to do. Catch it early and make
loud noises.

Cc: Alex Deucher <[email protected]>
Cc: Thierry Reding <[email protected]>
Cc: Rob Clark <[email protected]>
Cc: Sean Paul <[email protected]>
Cc: Manasi Navare <[email protected]>
Cc: [email protected]
Reviewed-by: Thierry Reding <[email protected]>
Reviewed-by: Alex Deucher <[email protected]>
Reviewed-by: Manasi Navare <[email protected]>
Signed-off-by: Jani Nikula <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]