amd64_edac: Correct node interleaving removal

When node interleaving is enabled, a subset of the addr[14:12] bits has
to be removed in order to get the normalized DCT address of the DRAM
channel. The actual number of bits to remove is determined by F1x[1,
0][7C:40][IntlvEn]. Do this correctly.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>