Bug970187, Bug970187, CDMA-3way calls

It correspondence of reviews.
https://github.com/mozilla-b2g/gaia/pull/19976

https://bugzilla.mozilla.org/show_bug.cgi?id=970187
I'm not sure CDMA_CALLS_LIMIT is a good name but I don't really know CDMA so I can't make a good recommendation. @gabrielesvelto , do you have a suggestion?