drm/i915/hdcp: Use both bits for device_count

Smatch spotted:
drivers/gpu/drm/i915//intel_hdcp.c:1406 hdcp2_authenticate_repeater_topology() warn: should this be a bitwise op?

and indeed looks to be suspect that we do need to use a bitwise or to
combine the two register fields into one counter.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190517102225.3069-3-chris@chris-wilson.co.uk