a_iface: s/Abis/L3/ for speech version/preference fields

There is no encoding of speech version / preference on Abis, only
on L3.  L3 is carried on Um, Abis and A.  Hence, referrin to Abis
in function names and comments is irritating.

Change-Id: Id226cd1414ca2a92356801bc71f43102d03ba37e
1 file changed