NEG bit default is '1' for external MDIOs as per FMAN-v3 RM, but on some
platforms, e.g. T2080QDS, this bit is '0', which leads to MDIO failure
on XAUI PHY, so set this bit definitely to align with the RM.
Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: York Sun <yorksun@freescale.com>
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