defxx: Fix !DYNAMIC_BUFFERS compilation warnings

This fixes compilation warnings:

drivers/net/fddi/defxx.c:294: warning: 'dfx_rcv_flush' declared inline after being called
drivers/net/fddi/defxx.c:294: warning: previous declaration of 'dfx_rcv_flush' was here
drivers/net/fddi/defxx.c:2854: warning: 'my_skb_align' defined but not used

triggered when the driver is built with DYNAMIC_BUFFERS undefined.  Code
tested to work just fine with these changes and a few DEFPA and DEFTA
boards.

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