clk: qoriq: Fix checkpatch type ALLOC_WITH_MULTIPLY

WARNING:ALLOC_WITH_MULTIPLY: Prefer kcalloc over kzalloc with multiply
+       subclks = kzalloc(sizeof(struct clk *) * count, GFP_KERNEL);

Signed-off-by: Emil Medve <Emilian.Medve@Freescale.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>