i7core_edac: Fix ecc enable shift

From: Keith Mannthey <kmannth@us.ibm.com>

Simple correction to a shift value.
ECC_ENABLED is bit 4 of MC_STATUS, Dev 3 Fun 0 Offset 0x4c

This correctly identifies the state of the ECC at the machine.

Signed-off-by: Keith Mannthey <kmannth@us.ibm.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>