drm/i915/hdcp: Allocate stream id after HDCP AKE stage

Allocate stream id after HDCP AKE stage and not before so that it
can also be done during link integrity check.
Right now for MST scenarios LIC fails after hdcp enablement for this
reason.

--v2
-no need for else block in prepare_streams function [Ankit]

--v3
-remove intel_hdcp argument from required_content_stream function
[Ankit]

Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240226063051.1685326-6-suraj.kandpal@intel.com