Previously we falsely relied on the PHY driver to unconditionally
enable the internal RX delay. Since the following fix for the PHY
driver this is not the case anymore:

commit 7b005a17 ("net: phy: mscc: configure both RX and TX internal
delays for RGMII")

In order to enable the delay we need to set the connection type to
"rgmii-rxid". Without the RX delay the ethernet is not functional at
all.

Fixes: 8668d8b2 ("arm64: dts: Add the Kontron i.MX8M Mini SoMs and baseboards")
Cc: stable@vger.kernel.org
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>