anv/blorp: Use the correct size for vkCmdCopyBufferToImage

anv/blorp: Use the correct size for vkCmdCopyBufferToImage

Now that we're using an uncompressed format for the buffer, we have to
scale down the dimensions we pass into BLORP when doing buffer->image
copies.

Fixes: dd92179a72 "anv: Canonicalize buffer formats for image/buffer..."
Closes: #2452
Reviewed-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3664>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3664>