drm/i915/dp: Send only a single modeset-retry uevent for a commit

There are multiple failure cases a modeset-retry uevent can be sent for
a link (TBT tunnel BW allocation failure, unrecoverable link training
failure), a follow-up patch adding the handling for a new case where the
DP MST payload allocation fails. The uevent is the same in all cases,
sent to all the connectors on the link, so in case of multiple failures
there is no point in sending a separate uevent for each failure; prevent
this, sending only a single modeset-retry uevent for a commit.

Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240722165503.2084999-7-imre.deak@intel.com