i965: Split brw_emit_reloc into brw_batch_reloc and brw_state_reloc.

i965: Split brw_emit_reloc into brw_batch_reloc and brw_state_reloc.

brw_batch_reloc emits a relocation from the batchbuffer to elsewhere.
brw_state_reloc emits a relocation from the statebuffer to elsewhere.

For now, they do the same thing, but when we actually split the two
buffers, we'll change brw_state_reloc to use the state buffer.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>