RAS/CEC: Add CONFIG_RAS_CEC_DEBUG and move CEC debug features there

The pfn and array files in (debugfs)/ras/cec are intended for debugging
the CEC code itself. They are not needed on production systems, so the
default setting for this CONFIG option is "n".

 [ bp: Have it with less ifdeffery by using IS_ENABLED(). ]

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>