drm/i915/dp: Compute DP tunnel BW during encoder state computation

Compute the BW required through a DP tunnel on links with such tunnels
detected and add the corresponding atomic state during a modeset.

v2:
- Fix error check of intel_dp_tunnel_compute_stream_bw(). (Ville)
- Move intel_dp_tunnel_atomic_cleanup_inherited_state() to this patch.
  (Ville)
- Move intel_dp_tunnel_atomic_clear_stream_bw() to this patch.

Reviewed-by: Uma Shankar <uma.shankar@intel.com> (v1)
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240220211841.448846-16-imre.deak@intel.com