ARM: mvebu: add devtmpfs to mvebu_v5_defconfig

The devtmpfs filesystem is now widely used and generally needed to
boot Linux systems. 42 ARM defconfigs have it enabled, so it makes
sense to have it enabled as well in mvebu_v5_defconfig.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lkml.kernel.org/r/1404375830-22169-2-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>