ideapad-laptop: Constify DMI table for real!

ideapad-laptop: Constify DMI table for real!

This is a follow-up patch to commit 49458e83082d ("ideapad-laptop:
Constify DMI table and other r/o variables") to do what its commit
message says. The actual commit differs from the patch posted at
https://www.mail-archive.com/platform-driver-x86@vger.kernel.org/msg05340.html
significantly, probably due to a bad merge conflict resolution. Fix up
the mess and constify the DMI table for real and fix the bogus
double-const of ideapad_rfk_data[].

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Matthew Garrett <matthew.garrett@nebula.com>
Cc: Ike Panhc <ike.pan@canonical.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>