There are a couple of words in The Etymologies from the 1930s that seem to indicate primitive ls could become ll in Quenya:
In addition, there is an “assimilated locative” form menelle “in Heaven” from Quenya prayers written in the 1950s (VT43/16) which is very likely derived from menel + sē, and thus represents a similar phonetic development.
However, in both the the Outline of Phonetic Development from the 1930s (OP1, PE19/47) and the Outline of Phonology from the 1950s (OP2, PE19/99) Tolkien said that primitive ls survived unchanged in Quenya. There are several Quenya words that demonstrate this ls survival: malsa (PE19/101), nelsat and tolsat (VT48/11). Thus it seems Tolkien vacillated on the exact development of primitive ls in Quenya.
There are very few examples of s-suffixes in Quenya, so finding examples and counter-examples of this sound change are difficult.