3cSOHO100-TX needs EXTRA_PREAMBLE

The 3cSOHO100-TX needs a mdio_sync() before mdio_read() to read the MII
transceiver registers properly.  Adding EXTRA_PREAMBLE to drv_flags of the
3cSOHO100-TX will force this.

This problem exists already for years (I checked back to 2.6.8).
Setting duplex for the 3cSOHO100-TX was more or less a random process.
Till 2.6.15 it was more likely that the diver ends up in half
duplex mode, after the code change in 2.6.16 it was more likely
to end up in full duplex mode. I wonder why nobody noticed this earier.

Hopefully addresses

Bug 7454 3c59x (3cSOHO100-TX Hurricane) slow network bug
http://bugzilla.kernel.org/show_bug.cgi?id=7454

and

Bug 3654 3cSOHO100-TX: No MII transceiver present
http://bugzilla.kernel.org/show_bug.cgi?id=3654

Cc: Jonas Sandberg <jonassa@gmail.com>
Cc: Jon Sanchez <bugs@niluje.net>
Signed-off-by: Steffen Klassert <klassert@mathematik.tu-chemnitz.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>