drm/i915/display: Implement infoframes readback for LSPCON

Implemented Infoframes enabled readback for LSPCON devices.
This will help align the implementation with state readback
infrastructure.

v2: Added proper bitmask of enabled infoframes as per Ville's
recommendation.

v3: Added pcon specific infoframe types instead of using the HSW
one's, as recommended by Ville.

v4: Addressed Ville's review comment by adding HDMI infoframe
versions directly instead of DIP wrappers.

v5: Re-ordered the patches to avoid potential break in usage,
as suggested by Ville.

Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201130204738.2443-13-uma.shankar@intel.com