PM/devfreq: Do not switch governors from sysfs when device is suspended

There is a possibility to switch the governors from sysfs even when the
device is in suspended state. This can cause a NOC error at times when
trying to access the device's monitor registers in a suspended state. This
change fixes this issue. Introduce a variable dev_suspended to know if
the device is in suspended state or not. Check if the device is suspended
before switching the governor from sysfs.

Change-Id: I15055aa51daa35272be4667e5bafb8ccd7933098
Signed-off-by: Rama Aparna Mallavarapu <aparnam@codeaurora.org>