ibm_newemac: Added 16K Tx FIFO size support for EMAC4

Some of the EMAC V4 implementations support 16K Tx FIFOs. This
patch adds support for this functionality and fixes typos in the
Tx FIFO size error messages.

Signed-off-by: Dave Mitchell <dmitchell@appliedmicro.com>
Acked-by: Prodyut Hazarika <phazarika@appliedmicro.com>
Acked-by: Victor Gallardo <vgallardo@appliedmicro.com>
Acked-by: Loc Ho <lho@appliedmicro.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>