msm: ipa: add active clients logging hash table

Add implementation of active clients logging hash table.
hash table tracks reference count modifications of
ipa active clients. cat /sys/kernel/debug/ipa/active_clients
to view the hash table.

Change-Id: Icd4bafa4c2a862bc76fc73677317e235b2d70f52
Signed-off-by: Valery Gorohovsky <valeryg@codeaurora.org>