clk: socfpga: Use NULL instead of 0

'div_reg' is a pointer. Assign NULL instead of 0.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Dinh Nguyen <dinguyen@altera.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

diff --cc drivers/clk/socfpga/clk.c
Simple merge