vmwgfx: A number of damage fixes

vmwgfx: A number of damage fixes

A damage tracker was sometimes attached to a pixmap in the middle of an
operation. That meant that damage was never registered for that operation
which caused dirty-tracking to fail. Instead, add a damage tracker as
soon as we have storage attached to the pixmap.

Also, when a pixmap was resized, the dirty region trackers could become
stale, and cause DMA operation extending outside of the pixmap with
server crashes as a result. This commit fixes that.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>