acerhdf: driver didn't verify the pointers in which it got product information

Driver didn't verify the pointers in which it got product information back
from DMI; on QEMU one of the pointers came back null, which made the
driver crash and subsequently caused a kernel panic.

Signed-off-by: Rahul Chaturvedi <rkc@chromium.org>
Signed-off-by: Peter Feuerer <peter@piie.net>
Cc: Borislav Petkov <petkovbb@gmail.com>
Cc: Andreas Mohr <andi@lisas.de>
Cc: Len Brown <lenb@kernel.org>
Cc: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>