blorp: Turn anv_CmdCopyBuffer into a blorp_buffer_copy() helper.

I want to be able to copy between buffer objects using BLORP in the i965
driver.  Anvil already had code to do this, in a reasonably efficient
manner - first using large bpp copies, then smaller bpp copies.

This patch moves that logic into BLORP as blorp_buffer_copy(), so we
can use it in both drivers.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/intel/blorp/blorp.h

@@ -132,6 +132,12 @@ blorp_copy(struct blorp_batch *batch,
            uint32_t dst_x, uint32_t dst_y,
            uint32_t src_width, uint32_t src_height);
 
+void
+blorp_buffer_copy(struct blorp_batch *batch,
+                  struct blorp_address src,
+                  struct blorp_address dst,
+                  uint64_t size);
+
 void
 blorp_fast_clear(struct blorp_batch *batch,
                  const struct blorp_surf *surf, enum isl_format format,