cpufreq: mediatek: Fix NULL pointer dereference in mediatek-cpufreq

Fix following coccicheck error:
drivers/cpufreq/mediatek-cpufreq.c:464:16-23: ERROR: info is NULL but dereferenced.

Use pr_err instead of dev_err to avoid dereferring a NULL pointer.

Fixes: f52b16ba9fe4 ("cpufreq: mediatek: Use device print to show logs")
Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>