Merge branch 'mlxsw-add-spectrum-1-ip6gre-support'

Merge branch 'mlxsw-add-spectrum-1-ip6gre-support'

Petr Machata says:

====================
mlxsw: Add Spectrum-1 ip6gre support

Ido Schimmel writes:

Currently, mlxsw only supports ip6gre offload on Spectrum-2 and newer
ASICs. Spectrum-1 can also offload ip6gre tunnels, but it needs double
entry router interfaces (RIFs) for the RIFs representing these tunnels.
In addition, the RIF index needs to be even. This is handled in
patches #1-#3.

The implementation can otherwise be shared between all Spectrum
generations. This is handled in patches #4-#5.

Patch #6 moves a mlxsw ip6gre selftest to a shared directory, as ip6gre
is no longer only supported on Spectrum-2 and newer ASICs.

This work is motivated by users that require multiple GRE tunnels that
all share the same underlay VRF. Currently, mlxsw only supports
decapsulation based on the underlay destination IP (i.e., not taking the
GRE key into account), so users need to configure these tunnels with
different source IPs and IPv6 addresses are easier to spare than IPv4.

Tested using existing ip6gre forwarding selftests.
====================

Link: https://lore.kernel.org/r/cover.1670414573.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>