drm/i915/pxp: Add plane decryption support

Add support to enable/disable PLANE_SURF Decryption Request bit.
It requires only to enable plane decryption support when following
condition met.
1. PXP session is enabled.
2. Buffer object is protected.

v2:
- Used gen fb obj user_flags instead gem_object_metadata. [Krishna]

v3:
- intel_pxp_gem_object_status() API changes.

v4: use intel_pxp_is_active (Daniele)

v5: rebase and use the new protected object status checker (Daniele)

v6: used plane state for plane_decryption to handle async flip
    as suggested by Ville.

v7: check pxp session while plane decrypt state computation. [Ville]
    removed pointless code. [Ville]

v8 (Daniele): update PXP check

v9: move decrypt check after icl_check_nv12_planes() when overlays
    have fb set (Juston)

v10 (Daniele): update PXP check again to match rework in earlier
patches and don't consider protection valid if the object has not
been used in an execbuf beforehand.

Cc: Bommu Krishnaiah <krishnaiah.bommu@intel.com>
Cc: Huang Sean Z <sean.z.huang@intel.com>
Cc: Gaurav Kumar <kumar.gaurav@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Juston Li <juston.li@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com> #v9
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210924191452.1539378-14-alan.previn.teres.alexis@intel.com