Minimizing the synchronize_rcu() calls in SSR code flow

In some scenarios it has been observed that 20sec SSR timer expires before
the SSR completes. As there is synchronize_rcu() called each time before we
free the endpoint(ep) node, the system ends up waiting for rcu grace
period to end multiple times.

We collect all the nodes that need freeing in a new cleanup_list, and
free them together. This way we have to call synchronize_rcu() only once.

Change-Id: I123ef9d397c3daae0a378b126b6d827d6615da0e
Signed-off-by: Chinmay Agarwal <chinagar@codeaurora.org>