Since brgphy doesn't call mii_phy_setmedia(), there is no reason to
set any value to ifm_data. If brgphy ever to call mii_phy_setmedia(),
then the value of BRGPHY_S1000 | BRGPHY_BMCR_FDX will trigger KASSERT.

While here, remove the obfuscating macro and wrap long lines.

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