drivers: edac: change the macro definition

The edac framework maintains each cache level and its index is starting
from 0. In order to be consistent with the framework, update our macro
definition to start from index 0 as well.

Change-Id: Ide146e739067d4f06a56a967f1e5aa1f0ba765be
Signed-off-by: Runmin Wang <runminw@codeaurora.org>