drm: msm: attach devices to dma_buf based on ION flags

Attach the appropriate secure/non-secure context-bank
device based on secure/non-secure buffers.
For secure-display and secure-camera-preview buffers,
attach it with the MDP device which does not have IOMMU.
These are direct S2-translation buffers and does not
require S1/S2 translations of IOMMU. This is required
as during the secure-camera-preview/secure-display usecases,
the secure-context bank is detached and might leave
the IOMMU ops in an unknown state.

Change-Id: I457865461e6b57fa90fa58884d78dc813ed5f7ec
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>