EDAC/mc_sysfs: Increase legacy channel support to 16

EDAC/mc_sysfs: Increase legacy channel support to 16

Newer AMD systems can support up to 16 channels per EDAC "mc" device.
These are detected by the EDAC module running on the device, and the
current EDAC interface is appropriately enumerated.

The legacy EDAC sysfs interface however, provides device attributes for
channels 0 through 11 only. Consequently, the last four channels, 12
through 15, will not be enumerated and will not be visible through the
legacy sysfs interface.

Add additional device attributes to ensure that all 16 channels, if
present, are enumerated by and visible through the legacy EDAC sysfs
interface.

Signed-off-by: Avadhut Naik <avadhut.naik@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250916203242.1281036-1-avadhut.naik@amd.com