lwip: bump to v2.2.1

[miri64]

Contribution description

lwIP v2.2.1 came out this morning, so let's bump our package for it.

Testing procedure

I ran the same old loops for lwIP testing:

for ipv4 in 0 1; do
    for ipv6 in 0 1; do
        for board in native samr21-xpro; do
            for app in lwip_sock_ip lwip_sock_tcp lwip_sock_udp; do
                if [ $ipv4 == 0 ] && [ $ipv6 == 0 ]; then
                    continue;
                fi;
                BOARD=$board LWIP_IPV4=$ipv4 LWIP_IPV6=$ipv6 make -C tests/pkg/${app} -j flash test
            done;
        done;
    done;
done

I also ran the tests/pkg/lwip test for native and tested the IP/UDP/TCP functionality on a 6LoWPAN-capable board (samr21-xpro), so after this (and scrolling through the changes since v2.2.0 a little bit) I am confident, that this does not break things.

Issues/PRs references

[miri64]

I also ran the tests/pkg/lwip test for native

I had some hick-ups with that, but after a bisect which ended up on a pretty random commit (c700ead), I was not able to reproduce it in either current master or this branch.

[riot-ci]

Murdock results

✔️ PASSED

0bb4ed0 lwip: bump to v2.2.1

Success	Failures	Total	Runtime
10271	0	10271	10m:19s

Artifacts

• Documentation preview