FDDI: defza: Move SMT Tx data buffer declaration next to its skb

Move the temporary data buffer used when tapping into the SMT Tx queue
from the outer function level into the conditional block it's actually
used in and its containing skb is also declared, making the structure of
code better.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: David S. Miller <davem@davemloft.net>