drm/i915/dp: Send a link training modeset-retry uevent to all MST connectors

drm/i915/dp: Send a link training modeset-retry uevent to all MST connectors

Send a modeset-retry uevent to all connectors in the same MST topology
after a link training failure and reduction of the link parameters. This
matches the way the same uevent is sent after a DP tunnel BW allocation
failure.

v2: Add NOTE that the atomic state may not be valid for SST links and
    assert that it's valid for MST links. (Ville)

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
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/20240610164933.2947366-11-imre.deak@intel.com