i5000: Fix the memory size calculation with 2R memories

When 2R memories are found, the memory size should be multiplied
by two, otherwise, it will report half of the memory size:

       +-----------------------------------------------+
       |                      mc0                      |
       |        branch0        |        branch1        |
       | channel0  | channel1  | channel0  | channel1  |
-------+-----------------------------------------------+
slot3: |     0 MB  |     0 MB  |     0 MB  |     0 MB  |
slot2: |     0 MB  |     0 MB  |     0 MB  |     0 MB  |
-------+-----------------------------------------------+
slot1: |     0 MB  |     0 MB  |     0 MB  |     0 MB  |
slot0: |  1024 MB  |  1024 MB  |  1024 MB  |  1024 MB  |
-------+-----------------------------------------------+

(the above machine have 4 x 2GB 2R memories)

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>