x86/intel_rdt: Support enter/exit of locksetup mode

The locksetup mode is the way in which the user communicates that the
resource group will be used for a pseudo-locked region. Locksetup mode
should thus ensure that all restrictions on a resource group are met before
locksetup mode can be entered. The resource group should also be configured
to ensure that it cannot be modified in unsupported ways when a
pseudo-locked region.

Introduce the support where the request for entering locksetup mode can be
validated. This includes: CDP is not active, no cpus or tasks are assigned
to the resource group, monitoring is not in progress on the resource
group. Once the resource group is determined ready for a pseudo-locked
region it is configured to not allow future changes to these properties.

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/b120f71ced30116bcc6c6f651e8a7906ae6b903d.1529706536.git.reinette.chatre@intel.com