msm: ipa3: Fix to null pointer access

After PM client deregister trying to access the PM handle causing the
NULL pointer access. Adding changes to avoid NULL pointer access.

Change-Id: Ieee7864989e8c54f09c8df659bfc91dca8e89b3b
Signed-off-by: Ashok Vuyyuru <avuyyuru@codeaurora.org>