drm/i915/dsc: Add slice_row_per_frame in DSC PPS programming

Add the newly added slice_row_per_frame parameter
in the Picture Parameter Set registers.
This defines the number of vertically stacked slices
in a frame.

Credits to Manasi for noticing bSpec change.

Suggested-by: Manasi Navare <manasi.d.navare@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181031001923.31442-1-manasi.d.navare@intel.com