The dw MAC requires that all clock domains to be running for it to
finish a MAC reset.  This include the clock provided by the PHY.

If the PHY is powered down, bit BMCR_PDOWN set, then it won't be
generating a clock.  And so the MAC never comes out of reset.  On
shutdown, Linux will put the PHY in powerdown mode, so it can easily
be the case that the PHY is powered down on boot.

See Linux kernel commit 2d871aa.

Currently the MAC reset is done before the phy is probed.  We can't
power up the phy until it's probed, so the resets must be in the
opposite order.  The MAC reset is in device init but the PHY probe is
in device open.  Device init is done first, always, while open is done
later, and only if the device is used.

Rather than move the phy probe to init, this moves the MAC reset to
open.  It seems better to speed up boots that doesn't use ethernet by
skipping MAC reset than to slow them down by adding PHY probe.

Signed-off-by: Trent Piepho <tpiepho@kymetacorp.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>