PM / devfreq: Strengthen check for freq_table

Since commit ea572f816032 ("PM / devfreq: Change return type of
devfreq_set_freq_table()"), all devfreq devices are expected to have a
valid freq_table. The devfreq core unconditionally dereferences
freq_table in the sysfs code and in get_freq_range().

Therefore, we need to ensure that freq_table is both non-null and
non-empty (length is > 0). If either check fails, replace the table
using set_freq_table() or return the error.

Signed-off-by: Samuel Holland <[e-mail]>
Signed-off-by: Chanwoo Choi <[e-mail]>

drivers/devfreq/devfreq.c

···
 		goto err_dev;
 	}
 
-	if (!devfreq->profile->max_state && !devfreq->profile->freq_table) {
+	if (!devfreq->profile->max_state || !devfreq->profile->freq_table) {
 		mutex_unlock(&devfreq->lock);
 		err = set_freq_table(devfreq);
 		if (err < 0)