EDAC: Add EDAC driver for DMC520

The driver supports error detection and correction on devices with an
ARM DMC-520 memory controller.

Signed-off-by: Lei Wang <leiwang_git@outlook.com>
Signed-off-by: Shiping Ji <shiping.linux@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: James Morse <james.morse@arm.com>
Link: https://lkml.kernel.org/r/83b48c70-dc06-d0d4-cae9-a2187fca628b@gmail.com