current ifmedia_entry, not from the user-supplied media word. The
user supplied media word may not necessarily match e.g. instance (if
the parent MAC driver is intentionally ignoring instance if its expecting
multiple PHYs with non-overlapping media, e.g. TI ThunderLAN) the media
word we are actually switching to.
Since PHY drivers use `instance' to determine if they should isolate
themselves, the ThunderLAN PHY was sometimes being incorrectly isolated
when in fact the user attempted to select that PHY (for e.g. BNC operation).
