EDAC: Correct DIMM capacity unit symbol

The {i3200|i7core|sb|skx}_edac drivers show DIMM capacity using the
wrong unit symbol: 'Mb' - megabit. Fix them by replacing 'Mb' with
'MiB' - mebibyte.

[Tony: These are all "edac_dbg()" messages, so this won't break scripts
       that parse console logs.]

Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-edac@vger.kernel.org
Link: https://lkml.kernel.org/r/20180919003433.16475-1-tony.luck@intel.com