msm: ocmem: Add infrastructure for interacting with TZ

In preparation for interacting with secure processor (TZ) refactor
the scheduler code to allow locking and unlocking ocmem regions
at allocation boundaries. This allows multiple segments to be
transferred in and out of a locked region and evict them
independently when required.

Change-Id: Ifd827a36e918aeb1f0802d82ca03c1e245598137
Signed-off-by: Naveen Ramaraj <nramaraj@codeaurora.org>