net: phy: dp83867: use 2ns delay if not specified in DTB

Most PHY drivers default to a 2ns delay if internal delay is requested
and no value is specified. Having a default value makes sense, as it
allows a Device Tree to only care about board design (whether there are
delays on the PCB or not), and not whether the delay is added on the MAC
or the PHY side when needed.

Whether the delays are actually applied is controlled by the
DP83867_RGMII_*_CLK_DELAY_EN flags, so the behavior is only changed in
configurations that would previously be rejected with -EINVAL.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Link: https://patch.msgid.link/e2509b248a11ee29ea408a50c231da4c1fa0863b.1746612711.git.matthias.schiffer@ew.tq-group.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>