i915/dp/dsc: Add DSC PPS register definitions

Display Stream Compression(DSC) has a set of Picture
Parameter Set(PPS) components that the encoder must
communicate to the decoder.

This patch adds register definitions to
the PPS parameters for eDP/MIPI case and Display Port.

v2:
- Use _MMIO_PIPE instead of _MMIO(_PICK()). (Manasi)
- Use DSC constants as arguments. (Manasi)

Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.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>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1531861861-10950-2-git-send-email-anusha.srivatsa@intel.com