EDAC: arm64: Fix CPU instance error reporting

The 'instance number' argument passed to the EDAC framework
error reporting functions needs to correspond to the ID of
the CPU which reported the error, rather than the ID of the
cache set/way where the error occurred.

Change-Id: Ice5039abe83756ef16726cc34b62b0b3c88e1e16
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>