Fix longstanding "error: storage size of '__mod_dmi_device_table' isn't known"

gcc 3.4.6 doesn't like MODULE_DEVICE_TABLE(dmi, x) expansion enough to
error out.  Shut it up in a most simple way.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>