EDAC/igen6: Fix the issue of no error events

Current igen6_edac checks for pending errors before the registration
of the error handler. However, there is a possibility that the error
occurs during the registration process, leading to unhandled pending
errors and no future error events. This issue can be reproduced by
repeatedly injecting errors during the loading of the igen6_edac.

Fix this issue by moving the pending error handler after the registration
of the error handler, ensuring that no pending errors are left unhandled.

Fixes: 10590a9d ("EDAC/igen6: Add EDAC driver for Intel client SoCs using IBECC")
Reported-by: Ee Wey Lim <ee.wey.lim@intel.com>
Tested-by: Ee Wey Lim <ee.wey.lim@intel.com>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20230725080427.23883-1-qiuxu.zhuo@intel.com