ANDROID: dma-buf: Add support to get flags associated with a buffer

Allow kernel clients to get the flags associated with a buffer
that is wrapped by a dma-buf. This information can be used to
communicate the type of memory associated with the
buffer(e.g. uncached vs cached memory).

Bug: 133508579
Test: ion-unit-tests
Change-Id: I82eab8beb738b258616c22a01080615d7ffb6ad5
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>
Signed-off-by: Sandeep Patil <sspatil@google.com>