PM / devfreq: Move declaration of DEVICE_ATTR_RW(min_freq)

Declaration of DEVICE_ATTR_RW(min_freq) is placed after function
max_freq_store. Move it to the correct place after min_freq_show.

Signed-off-by: Kamil Konieczny <k.konieczny@samsung.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>