Without this change the KSZ9477 Evaluation board's Linux (v6.5-rc1) shows
following device warning:

'ksz-switch spi1.0: Port 5 interpreting RGMII delay settings based on "phy-mode" property, please update device tree to specify "rx-internal-delay-ps" and "tx-internal-delay-ps"'

This is not critical, as KSZ driver by itself assigns default value of
tx delay to 2000 ps (as 'rgmii-txid' is set as PHY mode).

However, to avoid extra warnings in logs - the missing 'tx-internal-delay-ps'
has been specified with the default value of 2000 ps.
Signed-off-by: Lukasz Majewski <lukma@denx.de>
Link: https://lore.kernel.org/r/20230727080656.3828397-1-lukma@denx.deSigned-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>