e100: Fix ring parameter change handling regression.

When the PCI pool changes were added to fix resume failures:

commit 98468efd
e100: Use pci pool to work around GFP_ATOMIC order 5 memory allocation failu

and

commit 70abc8cb
e100: Fix broken cbs accounting due to missing memset.

This introduced a problem that can happen if the TX ring size
is increased.  We need to size the PCI pool using cbs->max
instead of the default cbs->count value.

Signed-off-by: David S. Miller <davem@davemloft.net>