i915: Correctly set the OQ counter bits.

i915: Correctly set the OQ counter bits.

While we may provide the extension, we need to tell applications that they
can't actually use it:

            An implementation can either set QUERY_COUNTER_BITS_ARB to the
            value 0, or to some number greater than or equal to n.  If an
            implementation returns 0 for QUERY_COUNTER_BITS_ARB, then the
            occlusion queries will always return that zero samples passed the
            occlusion test, and so an application should not use occlusion
            queries on that implementation.