i2c-hid: properly terminate i2c_hid_dmi_desc_override_table[] array

Commit 9ee3e066

 ("HID: i2c-hid: override HID descriptors for certain
devices") added a new dmi_system_id quirk table to override certain HID
report descriptors for some systems that lack them.

But the table wasn't properly terminated, causing the dmi matching to
walk off into la-la-land, and starting to treat random data as dmi
descriptor pointers, causing boot-time oopses if you were at all
unlucky.

Terminate the array.

We really should have some way to just statically check that arrays that
should be terminated by an empty entry actually are so.  But the HID
people really should have caught this themselves, rather than have me
deal with an oops during the merge window.  Tssk, tssk.

Cc: Julian Sax <jsbc@gmx.de>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>