screen-share: get previous_damage from data argument instead of weston_output

Instead of getting previous_damage from the weston_output struct, get it from
the frame_signal data argument. This will make possible to remove
previous_damage from weston_output after we decide what to do with
output->previous_damage usage in DRM backend.

Signed-off-by: Leandro Ribeiro <leandrohr@riseup.net>
3 jobs for cleanup_framesignal in 1 minute and 51 seconds (queued for 6 minutes and 47 seconds)
Status Job ID Name Coverage
  Container Prep
passed #1027030
container_prep

00:00:24

 
  Build
passed #1027031
build-native-meson-default-options

00:01:27

passed #1027032
build-native-meson-no-gl-renderer

00:00:26