arm64: dts: imx95-15x15-evk: fix the overshoot issue of NETC

The overshoot of MDIO, MDC, ENET1_TDx and ENET2_TDx is too high, so
reduce the drive strength of these pins.

Fixes: e3e8b199 ("arm64: dts: imx95: Add imx95-15x15-evk support")
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>