drm/vmwgfx: Remove call to reservation_object_test_signaled_rcu before wait

Since fence_wait_timeout_reservation_object_wait_timeout_rcu() with a
timeout of 0 becomes reservation_object_test_signaled_rcu(), we do not
need to handle such conversion in the caller. The only challenge are
those callers that wish to differentiate the error code between the
nonblocking busy check and potentially blocking wait.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sinclair Yeh <syeh@vmware.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Signed-off-by: Sinclair Yeh <syeh@vmware.com>