dt-bindings: net: ethernet-controller: Fix formatting error

When moving the *-internal-delay-ps properties to only apply for RGMII
interface modes there where a typo in the text formatting.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>