drm/i915: HDCP: fix Ri prime check done during link check

The check was always succeeding even in case of a mismatch due to the
HDCP_STATUS_ENC bit being set. Make sure both bits are actually set.

Signed-off-by: Oliver Barta <oliver.barta@aptiv.com>
Fixes: 2320175f

 ("drm/i915: Implement HDCP for HDMI")
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200328104100.12162-1-oliver.barta@aptiv.com