kernel - MPSAFE work - Remove unneeded token acquire/releases in vm_mmap.c

kernel - MPSAFE work - Remove unneeded token acquire/releases in vm_mmap.c

Many calls in vm_mmap did not need to hold the vm_token; the underlying
vm_map_* calls are self-synchronizing via a lockmgr lock on the map itself and
the rest of the calls were synchronized by taking tokens.

Comment the remaining token acquires/releases.

'Less Lock, More Rock'