drm/msm: handle dma_buf attach/map for secure buffers

During addfb2 ioctl, buffer is always attached to non-secure context bank.
At commit time when the plane property tells the buffer is secure
it needs to be attached and map to the secure context bank.
This change detects the context bank type and maps the buffer accordingly.

Change-Id: Icf3697b31d5ae5d217846fbee16467af55529c86
Signed-off-by: Narendra Muppalla <NarendraM@codeaurora.org>