msm: ipa: fix for race condition in IPA RM timer destruction

This change will ensure that the timer context is not wiped
out till it is known that the work is canceled and no longer
running

Change-Id: I52050caf020deda4353d13bdf28683d910e9ac66
Signed-off-by: Ravi Gummadidala <rgummadi@codeaurora.org>