drm/i915/hdcp: Add HDCP 2.2 stream register

Add HDCP 2.2 DP MST HDCP2_STREAM_STATUS
and HDCP2_AUTH_STREAM register in i915_reg header.

B.Spec: 21780
B.Spec: 14410
B.Spec: 50573

v2
- Modified naming convention of HDCP2_STREAM_STATUS
  for pre-gen12 platforms inline with B.Spec.

Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Tested-by: Karthik B S <karthik.b.s@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210111081120.28417-17-anshuman.gupta@intel.com