resctrl: Do not calculate free bandwidth for MBA

resctrl: Do not calculate free bandwidth for MBA

For CAT we calculate unallocated parts of the cache, however with MBA this does
not make sense as the purpose of that is to limit the bandwidth and the setting
is only proportional relative to bandwidth settings for other groups.

This means it makes sense to set the values to 100% even if there are other
groups with some allocations and that we don't need to find the available
(unallocated) bandwidth in all the groups.

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>