Add a new config option CONFIG_INTEL_IOMMU_DEBUGFS and do the base
enabling for Intel IOMMU debugfs.

Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Co-Developed-by: NGayatri Kammela <gayatri.kammela@intel.com>
Signed-off-by: NGayatri Kammela <gayatri.kammela@intel.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: NLu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: NSohil Mehta <sohil.mehta@intel.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>