arm64: dts: marvell: add generic-ahci compatibles for CP110 ahci

Testing with an Armada 8040 board shows that adding the generic-ahci
compatible to the CP110 AHCI nodes gets us working AHCI on the board.
A previous patch series posted by Thomas Petazzoni was retracted when
it was realised that the IP was supposed to be, and is, compatible
with the standard register layout.

Add this compatible.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>