msm: ipa3: rm: enhance inactivity timer logic

The current implementation of IPA RM inactivity timer is to set
or cancel the inactivity timer per TX packet to IPA.
For better performance, instead of canceling the timer, a flag is set
to indicate that timer needs to be set again after expiration.
In this was the setting the inactivity timer happens on control path
every 1 second instead of on data path on each TX packet to IPA.

Change-Id: I69ff587fe41034b68a8f083e41bdac1f148bf584
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>