net: mvpp2: use a data size of 10kB for Tx FIFO on port 0

This patch sets the Tx FIFO data size on port 0 to 10kB. This prepares
the PPv2 driver for the Jumbo frame support addition as the hardware
will need big enough Tx FIFO buffers when dealing with frames going
through an interface with an MTU of 9000.

Signed-off-by: Yan Markman <ymarkman@marvell.com>
[Antoine: commit message, small reworks.]
Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>