i5000_edac: Fix the logic that retrieves memory information

The logic there is broken: it basically creates two csrows for
each DIMM and assumes that all DIMM's are dual rank. Only one of
the csrows will contain the entire DIMM size. If single rank
memories are found, they'll be marked with 0 bytes.

The check if the AMB is present were also wrong.

Yet, as the error reports don't use the memory size in order to
credit an error to the right DIMM, that part of the driver seems
to work. That's why probably nobody detected the issue yet.

After this patch, the memory layout is now properly reported,
when debug mode is enabled, and the number of ranks per dimm is
now shown:

calculate_dimm_size: ----------------------------------------------------------
calculate_dimm_size: slot  3       0 MB   |    0 MB   |    0 MB   |    0 MB   |
calculate_dimm_size: slot  2       0 MB   |    0 MB   |    0 MB   |    0 MB   |
calculate_dimm_size: ----------------------------------------------------------
calculate_dimm_size: slot  1       0 MB   |    0 MB   |    0 MB   |    0 MB   |
calculate_dimm_size: slot  0     512 MB 1R|  512 MB 1R|  512 MB 1R|  512 MB 1R|
calculate_dimm_size: ----------------------------------------------------------
calculate_dimm_size:            channel 0 | channel 1 | channel 2 | channel 3 |
calculate_dimm_size:                   branch 0       |        branch 1       |

(1R above means that all memories on my test machine are single-ranked)

Reviewed-by: Aristeu Rozanski <arozansk@redhat.com>
Cc: Doug Thompson <norsk5@yahoo.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>