drm/dp/mst: change MST detection scheme

drm/dp/mst: change MST detection scheme

1. Get edid for all connected MST displays, not only on logical ports,
   in the same thread as MST topology detection is done:
     There are displays that have branches inside w/o logical ports.
     So in case another SST display connected downstream system can
     end-up in situation when 3 DOWN requests sent: two for
    ‘remote i2c read’ and one for ‘enum path resources’, making slots full.

2. Call notification callback in one place in the end of topology discovery/update:
     This is done to reduce number of events sent to userspace in case complex
     topology discovery is going, adding multiple number of connectors;

3. Remove notification callback call from short pulse interrupt processing function:
     This is done in order not to block interrupt processing function, in case any
     MST request will be made from it. Notification will be send from topology
     discovery/update work item.

Signed-off-by: Mykola Lysenko <[email protected]>
Reviewed-by: Harry Wentland <[email protected]>
Cc: [email protected]
Acked-by: Alex Deucher <[email protected]>
Signed-off-by: Dave Airlie <[email protected]>