PM / devfreq: Add timer type to devfreq_summary debugfs

The commit 4dc3bab8 ("PM / devfreq: Add support delayed timer for
polling mode") supports the delayed timer but this commit missed
the adding the timer type to devfreq_summary debugfs node.
Add the timer type to devfreq_summary debugfs.

Fixes: 4dc3bab8 ("PM / devfreq: Add support delayed timer for polling mode")
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>