perf bench numa: Use numa_node_to_cpus() to bind tasks to nodes

perf bench numa: Use numa_node_to_cpus() to bind tasks to nodes

It is currently assumed that each node contains at most nr_cpus/nr_nodes
CPUs and nodes' CPU ranges do not overlap.

That assumption is generally incorrect as there are archs where a CPU
number does not depend on to its node number.

This update removes the described assumption by simply calling
numa_node_to_cpus() interface and using the returned mask for binding
CPUs to nodes.

Also, variable types and names made consistent in functions using
cpumask.

Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Balamuruhan S <bala24@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Satheesh Rajendran <sathnaga@linux.vnet.ibm.com>
Link: http://lore.kernel.org/lkml/20200813113247.GA2014@oc3871087118.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>