ARM: mvebu: fix second and third PCIe unit of Armada XP mv78260

mv78260 flavour of Marvell Armada XP SoC has 3 PCIe units. The
two first units are both x4 and quad x1 capable. The third unit
is only x4 capable. This patch fixes mv78260 .dtsi to reflect
those capabilities.

Signed-off-by: Arnaud Ebalard <arno@natisbad.org>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: <stable@vger.kernel.org> # v3.10.x
Signed-off-by: Jason Cooper <jason@lakedaemon.net>