perf tools: Update Makefile with some help

The perf makefile is nicely complete except for

a) an uninstall option
b) a 'make help' description

This patch implements b)
it also comments out other non-working makefile targets

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>