ARM: imx: clk: No need to initialize phandle struct

commit 84344b43c (ARM: i.MX5: Allow DT clock providers) introduce the following
sparse warning:

arch/arm/mach-imx/clk.c:12:43: warning: Using plain integer as NULL pointer

There is no need to initialize phandle, so remove it.

Cc: Martin Fuzzey <mfuzzey@parkeon.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>