PM / devfreq: qoslat: implement get_dev_status()

The qoslat devfreq device does not implement the
get_dev_status() devfreq profile API. This will
lead to a crash if a governor tries to invoke
devfreq_update_stats(). Implement the API to prevent
this from happening.

Change-Id: I668c3b55a1585d8eb561da03475e1567b194feef
Signed-off-by: Amir Vajid <avajid@codeaurora.org>