IB/ipath: iba6110 rev4 no longer needs recv header overrun workaround

iba6110 rev3 and earlier had a chip bug where the chip could overrun the
recv header queue. rev4 fixed this chip bug so userspace no longer needs
to workaround it.  Now we only set the workaround flag for older chip
versions.

Signed-off-by: Arthur Jones <arthur.jones@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>