staging: ion: chunk_heap: use pr_debug for heap creation print

We're currently printing to the kernel log at `info' level when we
successfully create the chunk heap, but success messages should be done
at `debug' level.  Fix this.

Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>