staging: ion: remove order argument from free_buffer_page()

Now that the pages returned from the pool are compound pages, we do not
need to pass the order information to free_buffer_page().

Signed-off-by: Heesub Shin <heesub.shin@samsung.com>
Reviewed-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>