Fix Makefile.docker not to specify --load and --push flags at once
Fix Makefile.docker not to specify --load and --push flags at once

After running `make docker-images-all`, make affords us to push
image by displaying the message like below.

Define "DOCKER_FLAGS=--push" to push the build results.

However, when we specify `DOCKER_FLAGS=--push` without ARCH,
it conflicts with the docker buildx --load option which is
specified by default. Fix Makefile.docker not to specify
--load when --push is given.

Signed-off-by: Yutaro Hayakawa <59bee67a18a3499e71d504c11f6a4bd79135f5fb@gmail.com>

michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium