numa: make -numa parser dynamically allocate CPUs masks

so it won't impose an additional limits on max_cpus limits
supported by different targets.

It removes global MAX_CPUMASK_BITS constant and need to
bump it up whenever max_cpus is being increased for
a target above MAX_CPUMASK_BITS value.

Use runtime max_cpus value instead to allocate sufficiently
sized node_cpu bitmasks in numa parser.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1479466974-249781-1-git-send-email-imammedo@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
[ehabkost: Added asserts to ensure cpu_index < max_cpus]
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>