mips: octeon: mrvl, cn73xx.dtsi: Add AHCI/SATA DT node

Add the AHCI compatible SATA DT node to the Octeon CN73xx dtsi file.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Aaron Williams <awilliams@marvell.com>
Cc: Chandrakala Chavva <cchavva@marvell.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>