present/wnmd: Translate update region to screen space

The region as passed in is in the source pixmap's coordinate space, so
intersecting it with the clipList (which is in screen space) resulted in
disappointment.

Fixes Firefox popups such as the hamburger menu when using the EGL
backend.

v2:
* Drop vblank->x/y_off from RegionTranslate call, since they're always
  0 here (present_wnmd_check_flip rejects flips for x/y_off != 0).

Reported-by: Robert Mader <robert.mader@posteo.de>
Tested-by: Robert Mader <robert.mader@posteo.de>
Reviewed-by: Olivier Fourdan <ofourdan@redhat.com>
Tested-by: Joakim Tjernlund <joakim.tjernlund@infinera.com> # v1
(cherry picked from commit 466b8b43)
3 jobs for server-1.20-branch in 4 minutes and 27 seconds
Status Job ID Name Coverage
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passed #5886302
debian-testing

00:00:32

 
  Build And Test
passed #5886303
autotools-build-and-test

00:03:55

passed #5886304
meson-build-and-test

00:01:29