Use only statically allocated data for PHY config packet transmission.
With the previous incarnation, some data wouldn't be freed if the packet
transmit callback was never called.

A theoretical drawback now is that, in PCs with more than one card,
card A may complete() for a waiter on card B.  But this is highly
unlikely and its impact not serious.  Bus manager B may reset bus B
before the PHY config went out, but the next phy config on B should be
fine.  However, with a timeout of 100ms, this situation is close to
impossible.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>