s2io: Using static const generally increases object text and decreases data size. It also generally decreases overall object size.

text	   data	    bss	    dec	    hex	filename
 109387	    389	  24432	 134208	  20c40	drivers/net/s2io.o.old
 109358	    389	  24432	 134179	  20c23	drivers/net/s2io.o.new
Signed-off-by: NJoe Perches <joe@perches.com>
Acked-by: NJon Mason <jon.mason@exar.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>