PM / devfreq: tegra30: Include appropriate header

It's not very correct to include mod_devicetable.h for the OF device
drivers and of_device.h should be included instead.

Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Peter Geis <pgwipeout@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>