drivers: net: fsl_enetc_mdio: return with time-out if HW is stuck

On some boards MDIO may get stuck if it detects echo on the line.  This is
a know hardware issue, there is a board fix for it.  In case we're running
on a board that doesn't have the fix, we don't want to loop here forever
and freeze U-Boot.

Signed-off-by: Alex Marginean <alexandru.marginean@nxp.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>