misc: apq8084_dock: NULL-terminate of_match_table

The DT of_match_table is missing the NULL entry that
is needed to terminate the table. Without this there
is a risk of corrupting memory.

CRs-fixed: 620821
Change-Id: I067d3a990d166c626b6ae4e9cdc406454ad52847
Signed-off-by: Jack Pham <jackp@codeaurora.org>