x86/intel_rdt: Provide pseudo-locking hooks within rdt_mount

Stephen Rothwell reported that the Cache Pseudo-Locking enabling and the
kernfs support for mounting with fs_context are conflicting.

In preparation for a conflict-free merge between the two repos some no-op
hooks are created within the RDT mount function being changed by the two
features. The goal is for this commit to be placed on a minimal no-rebase
branch to be consumed by both features.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Suggested-by: Al Viro <viro@ZenIV.linux.org.uk>
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
Cc: David Howells <dhowells@redhat.com>
Link: https://lkml.kernel.org/r/410697ead08978bd12111c0afc4ce9e7bd71a5fe.1529706536.git.reinette.chatre@intel.com