drm/i915/dp_tunnel: Simplify detection of link BW change

drm/i915/dp_tunnel: Simplify detection of link BW change

update_tunnel_state() checks whether a tunnel state change (e.g.
available tunnel bandwidth) affects the list of valid modes for the
sink connected through the tunnel. If so, its caller sends a hotplug
event so userspace can re-enumerate the modes.

A change in tunnel bandwidth does not affect the mode list if the
bandwidth was above the sink's DPRX bandwidth both before and after the
update, since in that case the effective bandwidth remains limited by
the DPRX.

As get_current_link_bw() via intel_dp_max_link_data_rate() already
returns bandwidth values clamped to the DPRX limit, the condition for
detecting a mode list change can be simplified to:

    old_bw != new_bw

Remove the explicit checks for whether the bandwidth was below the
maximum DPRX bandwidth before and after the update, and rely on the
clamped bandwidth values instead.

Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260219182823.926702-3-imre.deak@intel.com