mwifiex: fix misnomers in mwifiex_free_lock_list()

Despite the name (and meticulous comments), this function frees no
memory and does not touch any locks. All it does is "delete" the list
heads -- which just means they'll be dangling, and we'll need to re-init
them if we use them again.

It seems like this code would work OK as a sort of canary for using the
list after we've torn everything down, so it's fine to keep the code;
let's just get the name and comments to match what's actually happening.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>