mp_image: add missing field to mp_image_params_equals()

This is pretty obscure, so it didn't matter much. It still breaks
switching output levels at runtime, because the video output is not
reinitialized with the new params.
video/out: remove legacy colorspace stuff

Reduce most dependencies on struct mp_csp_details, which was a bad first
attempt at dealing with colorspace stuff. Instead, consistently use
mp_image_params.

Code which retrieves colorspace matrices from csputils.c still uses this
type, though.