EDAC/ie31200: Break up ie31200_probe1()

Split ie31200_probe1() into two helper functions to easily extend support
for multiple memory controllers.

No functional changes intended.

Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Tested-by: Gary Wang <gary.c.wang@intel.com>
Link: https://lore.kernel.org/r/20250310011411.31685-10-qiuxu.zhuo@intel.com