i965: Change intel_batchbuffer_reloc() into brw_emit_reloc().

i965: Change intel_batchbuffer_reloc() into brw_emit_reloc().

This renames intel_batchbuffer_reloc to brw_emit_reloc and changes the
parameter naming and ordering to match drm_intel_bo_emit_reloc().

For now, it's a trivial wrapper that accesses batch->bo.  When we
rework relocations, it will start doing actual work.

target_offset should be expanded to a uint64_t to match the kernel,
but for now we leave it as its original 32-bit type.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Jason Ekstrand <jason@jlekstrand.net>