cpufreq: mediatek: fix passing zero to 'PTR_ERR'

In order to prevent passing zero to 'PTR_ERR' in
mtk_cpu_dvfs_info_init(), we fix the return value of of_get_cci() using
error pointer by explicitly casting error number.

Signed-off-by: Jia-Wei Chang <jia-wei.chang@mediatek.com>
Fixes: 0daa4732

 ("cpufreq: mediatek: Link CCI device to CPU")
Reported-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>