msm: ipa: change ipa_active_clients locking scheme

As mutex_trylock() is not allowed in atomic context, ipa_active_clients is
now composed of a mutex, a spinlock and a boolean flag. The 'new'
synchronization object exposes a lock(), unlock() and trylock() API.

Change-Id: I75032d9d14d8598859d08a788d99ddb873ef58bf
Signed-off-by: Gidon Studinski <gidons@codeaurora.org>