netxen: fix lro buffer allocation

Alloc 12k skbuffs so that firmware can aggregate more
packets into one buffer. This doesn't raise memory
consumption since 9k skbs use 16k slab cache anyway.

Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>