Documentation: arm: misc updates to Marvell EBU SoC status

Following the merging of mach-kirkwood into mach-mvebu, the removal of
mach-kirkwood, and the progress of the integration of mach-dove into
mach-mvebu, this commit makes a few updates to the Marvell README file
in the kernel documentation.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lkml.kernel.org/r/1406227593-29749-3-git-send-email-thomas.petazzoni@free-electrons.com


Signed-off-by: Jason Cooper <jason@lakedaemon.net>