PM / devfreq: Remove unneeded conditional statement

The freq_table array of each devfreq device is always not NULL.
In result, it is unneeded to check whether profile->freq_table
is NULL or not.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>