EDAC/igen6: Add polling support

Some PCs with Intel N100 (with PCI device 8086:461c, DID_ADL_N_SKU4)
experienced issues with error interrupts not working, even with the
following configuration in the BIOS.

    In-Band ECC Support: Enabled
    In-Band ECC Operation Mode: 2 (make all requests protected and
                                   ignore range checks)
    IBECC Error Injection Control: Inject Correctable Error on insertion
                                   counter
    Error Injection Insertion Count: 251658240 (0xf000000)

Add polling mode support for these machines to ensure that memory error
events are handled.

Signed-off-by: Orange Kao <orange@aiven.io>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Link: https://lore.kernel.org/all/20241106114024.941659-3-orange@aiven.io