farsync: Fix compile warnings.

drivers/net/wan/farsync.c: In function 'fst_intr_rx':
drivers/net/wan/farsync.c:1312: warning: cast to pointer from integer of different size
drivers/net/wan/farsync.c: In function 'do_bottom_half_tx':
drivers/net/wan/farsync.c:1407: warning: cast to pointer from integer of different size

The "skb" and "mem" arguments being passed here are DMA addresses
being programmed into the hardware registers, so pass them as the type
that they actually are.  And use the correct printf formatting in
debug logging statements for these things to match the type change.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>