drm/vmwgfx: Schedule an fb dirty update after resume

We have had problems displaying fbdev after a resume and as a
workaround we have had to call vmw_fb_refresh(). This has had
a number of unwanted side-effects. The root of the problem was,
however that the coalesced fbdev dirty region was not empty on
the first dirty_mark() after a resume, so a flush was never
scheduled.

Fix this by force scheduling an fbdev flush after resume, and
remove the workaround.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Deepak Rawat <drawat@vmware.com>