i965: Drop the memcmp for finding duplicated CURBE uploads.

i965: Drop the memcmp for finding duplicated CURBE uploads.

At this point, the extra copy of the data and memcmp are as expensive as
just re-uploading.

Note: now that we'll always upload, and brw_constant_buffer watches
BRW_NEW_BATCH anyway, we don't need to explicitly unref the old curbe_bo
at batch reset time.

No significant performance difference on glamor copywinwin10 (n=55),
despite that test having a 98% hit rate on the cache.

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