Follow-up changes for intelrdt detection

[thaJeztah]

Posting as tracking issue, following #3485 (comment)

Hmm, there's one consideration that I don't know if we should care about here. If resctrlfs is mounted with -o cdp we will have L3CODE/ and L3DATA/ (instead of L3/) under the info/ dir.

I don't remember if CDP is officially supported in the runtime spec but I guess specifying something like L3DATA:0=ff\nL3CODE:0=ff in intelRdt.l3CacheSchema would work in practice.