Is there an info.plist key for advertising identifier use

No, but you can use Felix Krause’s https://fastlane.tools to fully or partially automate whole Delivery process (incl. passing this stupid IDFA Radio Button blocker amongst others).

No, there is nothing in the info.plist that's related to Advertising Identifier.

When you will submit the app to the App Store you'll need to check some things in order to inform Apple you are doing usage with the identifier. More details regarding that here:

https://developer.apple.com/library/ios/documentation/LanguagesUtilities/Conceptual/iTunesConnect_Guide/Chapters/SubmittingTheApp.html

Here is how to retrieve the Advertising Identifier:

Objective C -

@import AdSupport;

...

NSString *adId = [[[ASIdentifierManager sharedManager] advertisingIdentifier] UUIDString];

Swift -

import AdSupport

...

let myIDFA: String?
    // Check if Advertising Tracking is Enabled
    if ASIdentifierManager.shared().isAdvertisingTrackingEnabled {
        // Set the IDFA
        myIDFA = ASIdentifierManager.shared().advertisingIdentifier.uuidString
    } else {
        myIDFA = nil
    }

(updated to Swift 3.0)