drm/i915/dp: Add DSC params and DSC config to intel_crtc_state

Basic DSC parameters and DSC configuration data needs to be computed
for each of the requested mode during atomic check. This is
required since for certain modes, valid DSC parameters and config
data might not be computed in which case compression cannot be
enabled for that mode.
For that reason we need to add these params and config structure
to the intel_crtc_state so that if valid this state information
can directly be used while enabling DSC in atomic commit.

v2:
* Rebase on drm-tip (Manasi)

Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181128202628.20238-1-manasi.d.navare@intel.com