soc: qcom: mem-buf: Add support for suppliers to export dma-bufs

Currently, mem-buf suppliers can only provide a consumer with a memory
buffer if the consumer requests for the memory buffer, in which case
the supplier has no control over the contents of the buffer that is
given to the consumer. This is not ideal in cases where the supplier
virtual machine (VM) may have data that is of interest to the consumer,
which can be shared using a memory buffer.

Introduce a new IOCTL command which allows a client to specify a
dma-buf that they would like to share with a consumer VM, as well
as the access control rules that should be applied to the buffer.

Change-Id: I1e4ec1205ad4e69039ec0ab26b4209512896a354
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>