This adds the APM X-Gene SLIMpro mailbox device tree
node documentation.
Signed-off-by: NFeng Kan <fkan@apm.com>
Signed-off-by: NDuc Dang <dhdang@apm.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NJassi Brar <jaswinder.singh@linaro.org>