x86/intel_rdt: Init padding only if a device exists

If no device exists it's pointless to calculate the padding data for the
schemata files.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: ravi.v.shankar@intel.com
Cc: tony.luck@intel.com
Cc: fenghua.yu@intel.com
Cc: vikas.shivappa@intel.com