x86, MCE, AMD: Remove shared banks sysfs linking

The code used to create a symlink on all non-BSP cores of a node when
the MCi_MISCj bank is present once per node. (This is generally the
case with bank 4 on AMD). However, these sysfs links cause a bunch
of problems with cpu off-/onlining testing and are, as such, a bit
overengineered. IOW, there's nothing wrong with having normal sysfs
files for the shared banks since the corresponding MSRs are replicated
across each core anyway.

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