gpu: ion: Skip wrong usage check for secure buffers

With the change to secure buffers at allocation time, it is
no longer possible to correctly validate if the memory is
re-secured with a different usage hint. Considering the usage
hint is being deprecated anyway, drop the redundant check. If
a client tries to re-secure with the wrong usage hint, failures
will occur elsewhere to indicate the problem.

Change-Id: If8487c431eb4555927cd06c6cc5edcb1a66002f1
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>