net: fec_mxc: fix probing for imx8qxp

net: fec_mxc: fix probing for imx8qxp

probing on capricorn board (imx8qxp based) brings:

Can't find FEC0 clk rate: -19

Cause is that when probing fec_mxc driver, fec_mii_setspeed()
is called which calls fec_get_clk_rate().

fec_mii_setspeed() calls fec_get_clk_rate with NULL pointer
for udev and so as in IMX8QXP case CLK_CCF is enabled
udev gets searched with:

uclass_get_device_by_seq(UCLASS_ETH, idx, &dev);

but we do not have yet a UCLASS_ETH ! as we just probing it!

Prevent this by passing udev to fec_get_clk_rate()

Signed-off-by: Heiko Schocher <hs@denx.de>