EDAC/igen6: Add debugfs interface for Intel client SoC EDAC driver

Add debugfs support to fake memory correctable errors to test the
error reporting path and the error address decoding logic in the
igen6_edac driver.

Please note that the fake errors are also reported to EDAC core and
then the CE counter in EDAC sysfs is also increased.

Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>