ARM: dts: sunxi: Add a startup delay for fixed regulator enabled phys

It seems that recent kernels have a shorter timeout when scanning for
ethernet phys causing us to hit a timeout on boards where the phy's
regulator gets enabled just before scanning, which leads to non working
ethernet.

A 10ms startup delay seems to be enough to fix it, this commit adds a
20ms startup delay just to be safe.

This has been tested on a sun4i-a10-a1000 and sun5i-a10s-wobo-i5 board,
both of which have non-working ethernet on recent kernels without this
fix.

Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>