ion: Fix use after free during ION_IOC_ALLOC

If a user happens to call ION_IOC_FREE during an
ION_IOC_ALLOC on the just allocated id, and the
copy_to_user fails, the cleanup code will attempt
to free an already freed handle.

This adds a wrapper for ion_alloc that adds an
ion_handle_get to avoid this.

Bug: 31568617
Change-Id: I476e5bd5372b5178a213f1fea143d270cf9361ed
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Git-repo: https://android.googlesource.com/kernel/msm/


Git-commit: 20a5411d0115b16826f3d327b6abb0192c8a2001
Signed-off-by: Dennis Cagle <d-cagle@codeaurora.org>