x86/intel_rdt: Enable setting of exclusive mode

The new "mode" file now accepts "exclusive" that means that the
allocations of this resource group cannot be shared.

Enable users to modify a resource group's mode to "exclusive". To
succeed it is required that there is no overlap between resource group's
current schemata and that of all the other active resource groups as
well as cache regions potentially used by other hardware entities.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: fenghua.yu@intel.com
Cc: tony.luck@intel.com
Cc: vikas.shivappa@linux.intel.com
Cc: gavin.hindman@intel.com
Cc: jithu.joseph@intel.com
Cc: dave.hansen@intel.com
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/83642cbba3c8c21db7fa6bb36fe7d385d3b275f2.1529706536.git.reinette.chatre@intel.com