dts: marvell: add CM3 SRAM memory to cp11x ethernet device tree

CM3 SRAM address space will be used for Flow Control configuration.

Signed-off-by: Stefan Chulski <stefanc@marvell.com>
Signed-off-by: Konstantin Porotchkin <kostap@marvell.com>
Acked-by: Marcin Wojtas <mw@semihalf.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>