ARM: dts: imx6q-dhcom: Add ethernet VIO regulator

Add VIO regulator that supplies multiple ethernet magnetics and
currently there is no upstream support for that in the networking,
so just keep the regulator enabled always to emulate what other
boards, which have this hard-wired, do. Until there is support.

Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Marek Vasut <marex@denx.de>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: kernel@dh-electronics.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Shawn Guo <shawnguo@kernel.org>