So qxl has ioports, but it really really really doesn't want you
to write to them twice, but if you write and get a signal before
the irq arrives to let you know its completed, you have to think
ahead and avoid writing another time.

However this works fine for update area where really multiple
writes aren't the end of the world, however with create primary
surface, you can't ever do multiple writes. So this stop internal
kernel writes from doing interruptible waits, because otherwise
we have no idea if this write is a new one or a continuation of
a previous one.

virtual hw sucks more than real hw.

This fixes lockups and VM crashes when resizing and starting/stopping
X.
Signed-off-by: NDave Airlie <airlied@redhat.com>