i965: Order write of query availablity with earlier writes

i965: Order write of query availablity with earlier writes

Currently we signal the availabilty of the query result using an
unordered pipe-control write. As it is unordered, it may be executed
before the write of the query result itself - and so an observer may
read the query result too early. Fix this by requesting that the write
of the availablity flag is ordered after earlier pipe control writes.

Testcase: piglit/arb_query_buffer_object-qbo/*async*
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>