drm/i915/dp: Make intel_dp_can_join() static
intel_dp_can_join() was previously exposed in intel_dp.h, but after the
recent joiner refactor it is only used internally via
intel_dp_joiner_candidate_valid(). It no longer needs external
visibility, so make it static and drop the prototype from intel_dp.h.
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260205083623.793902-2-ankit.k.nautiyal@intel.com