For the RTL8211F PHY, configuration of RX/TXDLY was missing.
At least on my i.MX93 EVK, this is necessary for transmission
to work (RXDLY defaults to true on the PHY).
This commit brings support for RGMII internal delay configuration
(on or off for both directions) and enables it on the i.MX93 EVK
board. The introduced Kconfig is set to default to 'n', to avoid
breaking the functionality of other, out-of-tree boards based on
i.MX93, running the RTL8211F PHY, or to avoid introducing
unnecessary code on boards running other PHYs.
Configuration of internal delay on other PHYs is not
implemented, and results in a warning (but no error).
Signed-off-by: George Poulios <gpoulios@census-labs.com>