amd64_edac: Build module on x86-32

By popular demand, enable amd64_edac on 32-bit too.

Boris:
 - update Kconfig text.
 - add a warning on load which states that 32-bit configurations are unsupported.

Signed-off-by: Tomasz Pala <gotar@polanet.pl>
Link: http://lkml.kernel.org/r/20141102102212.GA7034@polanet.pl


Signed-off-by: Borislav Petkov <bp@suse.de>