PM / QoS: Free the memory allocated during add request

Allocated memory is not getting freed in remove request.
This change is to free the memory allocated to avoid memory
leaks.

Change-Id: I1225d492b7f58f8bda2621ec0bb2bd201d8dee6c
Signed-off-by: Srinivas Rao L <lsrao@codeaurora.org>