i915: Emit a single relocation per vbo

Reducing the number of relocations has lots of nice knock-on effects,
not least including reducing batch buffer size, auxilliary array sizes
(vmalloced and copied into the kernel), processing of uncached
relocations etc.

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

src/mesa/drivers/dri/i915/i915_fragprog.c

@@ -1422,6 +1422,10 @@ i915ValidateFragmentProgram(struct i915_context *i915)
                                               intel->vertex_attr_count,
                                               intel->ViewportMatrix.m, 0);
 
+      assert(intel->prim.current_offset == intel->prim.start_offset);
+      intel->prim.start_offset = (intel->prim.current_offset + intel->vertex_size-1) / intel->vertex_size * intel->vertex_size;
+      intel->prim.current_offset = intel->prim.start_offset;
+
       intel->vertex_size >>= 2;
 
       i915->state.Ctx[I915_CTXREG_LIS2] = s2;