drm/amd/display: add and use defines from drm_hdcp.h

[Why]
These defines/macros exist already no need to redefine them

[How]
Use the defines/macros from drm_hdcp.h

-we share the rxstatus between HDMI and DP (2 bytes), But upstream
defines/macros for HDMI are for 1 byte. So we need to create a separate
rxstatus for HDMI

Signed-off-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>