i965: Fix BRW_BATCH_STRUCT to specify RENDER_RING, not UNKNOWN_RING.

i965: Fix BRW_BATCH_STRUCT to specify RENDER_RING, not UNKNOWN_RING.

I missed this in the boolean -> enum conversion.  C cheerfully casts
false -> 0 -> UNKNOWN_RING.  On Gen4-5, this causes the render ring
prelude hook to get called in the middle of the batch, which is crazy.

BRW_BATCH_STRUCT is not used on Gen6+.

Fixes regressions since 395a32717df494353703f3581edcd3ba380f16d6
("i965: Introduce an UNKNOWN_RING state.").

Fixes "fips -v glxgears" on Ironlake.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>