edac i5000, i5400: fix pointer math in i5000_get_mc_regs()

"pvt->ambase" is a u64 datatype.  The intent here is to fill the first
half in the first call to pci_read_config_dword() and the other half in
the second.  Unfortunately the pointer math is wrong so we set the wrong
data.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>