drm/i915: Add CRTC output format YCBCR 4:2:0

drm/i915: Add CRTC output format YCBCR 4:2:0

Currently, we are using a bool in CRTC state (state->ycbcr420),
to indicate modeset, that the output format is YCBCR 4:2:0. Now in
order to support other YCBCR formats, we will need more such flags.

This patch adds a new enum parameter for YCBCR 4:2:0 outputs, in the
CRTC output formats and then plugs it during the modeset.

V3: Added this patch in the series, to address review comments from
    second patchset.
V4: Added r-b from Maarten (on v3)
    Addressed review comments from Ville:
        - Change the enum name to intel_output_format.
        - Start the enum value (INVALID) from 0 instaed of 1.
        - Set the crtc's output_format to RGB in encoder's compute_config.
V5: Broke previous patch 1 into two parts,
    - first patch to add CRTC output format in general
    - second patch (this one) to add YCBCR 4:2:0 output
      format specifically.
    - Use ARRAY_SIZE(format_str) for output format validity check (Ville)
V6: Added a separate function to calculate crtc_state->output_format, and
    calling it from various get_config function (Fix CI build warning)
V7: Fixed checkpatch warnings for alignment
V8: Rebase
V9: Rebase
V10: Rebase
V11: Addressed review comments from Ville:
	- Change check for CRTC output format from > ARRAY_SIZE to >= ARRAY_SIZE.
	- Check for values < INTEL_OUTPUT_FORMAT_RGB is unnecessary.
	- No need to get CRTC YCBCR config, for pre-BDW functions.
    Added Ville's r-b.

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1539325394-20788-2-git-send-email-shashank.sharma@intel.com