jme: Don't immediately recycle the TX descriptor even if it is owned by us.

jme: Don't immediately recycle the TX descriptor even if it is owned by us.

This chip will always update the TX descriptor's 32bits fields in order,
so even if the status field has been updated, i.e. OWN is cleared, it still
does not mean that the buflen field has been updated.  To avoid this race
we don't immediately recycle the currently checking TX descriptor.  Instead,
next TX descriptor's OWN bit is checked, if it is cleared, then the updating
of the currently checked TX descrptor is really done.

This is intended to fix the seldom watchdog timeout that was observed on this
chip.

Thank devinchiu@jmicron.com very much for providing necessary information.