drm/i915/hdcp: Refactor intel_dp_hdcp2_capable

Break intel_dp_hdcp2_capable so that the common the code can be
reused for the remote capability check.

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/20240223081453.1576918-5-suraj.kandpal@intel.com