ARM: dts: turris-omnia: remove unneeded status = "okay" properties

Only nodes which have status = "disabled" defined from included files
need status = "okay".

The ethernet-phy node and the i2cmux node do not need it, since they are
wholly defined here.

Signed-off-by: Marek Behún <kabel@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Uwe Kleine-König <uwe@kleine-koenig.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Gregory CLEMENT <gregory.clement@bootlin.com>
Cc: Andreas Färber <afaerber@suse.de>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>