tools: add tst_ncpus/_max api to get number of CPUS

Add tst_ncpus and tst_ncpus_max api to get the number of CPUS
online and configured.

Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Caspar Zhang <caspar@casparzhang.com>
7 files changed