vga: move computation of dirty memory region later

Move the computation of region_start and region_end after the value of
"bits" is known.  This makes it possible to distinguish modes that
support horizontal pel panning from modes that do not.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed