drm/i915/hdcp: HDCP2.x Refactoring to agnostic hdcp

There are more than 1 type of content protection security firmware.
Make the name generic
%s/_mei_/_

--v3
-Changing names to drop cp_fw to make naming more agnostic[Jani]

--v4
-remove header reference in intel_display_core.h [Uma]
-fix commit message and prefix drm [Uma]

Cc: Tomas Winkler <tomas.winkler@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230316092927.668980-4-suraj.kandpal@intel.com