powerpc: dts: t208x: Disable 10G on MAC1 and MAC2

There aren't enough resources to run these ports at 10G speeds. Disable
10G for these ports, reverting to the previous speed.

Fixes: 36926a7d ("powerpc: dts: t208x: Mark MAC1 and MAC2 as 10G")
Reported-by: Camelia Alexandra Groza <camelia.groza@nxp.com>
Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Reviewed-by: Camelia Groza <camelia.groza@nxp.com>
Tested-by: Camelia Groza <camelia.groza@nxp.com>
Link: https://lore.kernel.org/r/20221216172937.2960054-1-sean.anderson@seco.com


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