Add ETH_400GBASE_PSM4 PMD type to openconfig-transport-types

[atmanmehta]

[Note: Before this PR can be reviewed please agree to the CLA covering this repo. Please also review the contribution guide - https://github.com/openconfig/public/blob/master/doc/external-contributions-guide.md]

Change Scope

• Add ETH_400GBASE_PSM4 PMD type to openconfig-transport-types.
• This change is backward compatible.

Platform Implementations

Adding this since it is already an industry standard.

[OpenConfigBot]

Compatibility Report for commit fa313467c9a117f20e85816c18797961169792db: ⛔ yanglint@SO 1.10.17

[dplore]

@ejbrever can you review this one for us?

[ejbrever]

In discussing with a @thofmeister it sounds like this 400G PSM4 is really DR4 which we already have here: https://github.com/openconfig/public/blob/master/release/models/optical-transport/openconfig-transport-types.yang#L1042

Is there a reason that wouldn't work? Thanks.

[atmanmehta]

Based on discussions with @ejbrever and @thofmeister, changed the type to ETH_400GMSA_PSM4. PTAL.

[ejbrever]

I'm good with this, but as I'm not nearly as close to optics as tad@, I'll leave the final LGTM to him.

[thofmeister]

ETH_400GMSA_PSM4 LGTM.

Thanks, Tad

[dplore]

/gcbrun