i965: Unify query object BO reallocation code.

i965: Unify query object BO reallocation code.

If we haven't allocated a BO yet, we need to do that.  Or, if there
isn't enough room to write another pair of values, we need to gather up
the existing results and start a new one.  This is simple enough.

However, the old code was awkwardly split into two blocks, with a
write_depth_count() placed in the middle.  The new depth count isn't
relevant to gathering the old BO's data, so that can go after the
reallocation is done.  With the two blocks adjacent, we can merge them.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>