i7core_edac: Fix order of lines in i7core_register_mci

The flag is_registered is not initialized until mci_bind_devs()
is called.  Refer it properly.

The mci->dev and mci->edac_check is required in edac_mc_add_mc(),
so prepare them just before the call.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>