msm: camera: memmgr: Remove the region flag from request_mem API

Remove the region flag from the cam_mem_mgr_request_mem() API because
it is redundant and the same information can be conveyed using the
flags parameter in the input request descriptor of the API. Do this
because only the camera SMMU driver needs to be aware of memory regions
and the memory manager driver which sits on top of camera SMMU driver
need not be aware of underlying memory regions inside the IOVA address
space of individual hardware blocks.

Change-Id: Ic2e737ae36dc1ff05663d6f47ca1207b8a784877
Signed-off-by: Seemanta Dutta <seemanta@codeaurora.org>