drm/i915/hdcp: return correct error code

hdcp2_enable_stream_encryption shouldn't get called in case
of any port authentication or encryption error, though
hdcp2_enable_stream_encryption checks for link encryption
before enabling stream encryption and returns error but
this return error code won't be correct in case of any error
due to port authentication and encryption.

Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210319100208.5886-4-anshuman.gupta@intel.com