make getting Chassis collection work with DPU BMCs

[iamsli]

This fixes the issue where we cannot get the Chassis collection for DPU BMCs.

Per Redfish docs, Controls should be a Link singular

Controls (v1.17+) { object The link to the collection of controls located in this chassis.
Contains a link to a resource.
@odata.id string read-only Link to Collection of Control. See the Control schema for
details.
}

Closes: #322

[stmcginnis]

Awesome, thanks for fixing it. Would you be able to pick up the other parts of #324? I'll close that one in favor of this PR.

Thanks!

[iamsli]

oh i didn't even see that PR. Just made those changes, thanks!

[stmcginnis]

Thanks!!