drm/i915: Allow planes to declare their minimum acceptable cdclk

drm/i915: Allow planes to declare their minimum acceptable cdclk

Various pixel formats and plane scaling impose additional constraints
on the cdclk frequency. Provide a new plane->min_cdclk() hook that
will be used to compute the minimum acceptable cdclk frequency for
each plane.

Annoyingly on some platforms the numer of active planes affects
this calculation so we must also toss in more planes into the
state when the number of active planes changes.

The sequence of state computation must also be changed:
1. check_plane() (updates plane's visibility etc.)
2. figure out if more planes now require update min_cdclk
   computaion
3. calculate the new min cdclk for each plane in the state
4. if the minimum of any plane now exceeds the current
   logical cdclk we recompute the cdclk
4. during cdclk computation take the planes' min_cdclk into
   accoutn
5. follow the normal cdclk programming to change the
   cdclk frequency. This may now require a modeset (except
   on bxt/glk in some cases), which either succeeds or
   fails depending on whether userspace has given
   us permission to perform a modeset or not.

v2: Fix plane id check in intel_crtc_add_planes_to_state()
    Only print the debug message when cdclk needs bumping
    Use dev_priv->cdclk... as the old state explicitly

Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191015193035.25982-5-ville.syrjala@linux.intel.com