linux: export hwloc_linux_get_tid_last_cpu_location()

This is equivalent to hwloc_get_proc_last_cpu_location(THREAD) on Linux,
but it's better for clarity to have this Linux specific call as well
(and it was already implemented internally)
hwloc-ps: Add -e/--get-last-cpu-location
hwloc-bind: Add -e as a synonym to --get-last-cpu-location

To match what hwloc-ps supports.
hwloc-ps: don't report locations as caches unless there is nothing equivalent

We report the higher object matching the binding.
Go down if it's a cache that has a single identical child.