batch: Specify number of relocations to accommodate

Since relocations are variable size, depending upon generation, it is
easier to handle the resizing of the batch request inside the
BEGIN_BATCH macro. This still leaves us with having to resize commands
in a few places - which still need adaption for gen8+.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

benchmarks/intel_upload_blit_large.c

@@ -97,7 +97,7 @@ do_render(drm_intel_bufmgr *bufmgr, struct intel_batchbuffer *batch,
 	drm_intel_bo_subdata(src_bo, 0, sizeof(data), data);
 
 	/* Render the junk to the dst. */
-	BLIT_COPY_BATCH_START(batch->devid, 0);
+	BLIT_COPY_BATCH_START(0);
 	OUT_BATCH((3 << 24) | /* 32 bits */
 		  (0xcc << 16) | /* copy ROP */
 		  (width * 4) /* dst pitch */);