octeontx2-af: cn10K: Add MTU configuration

OcteonTx3 CN10K silicon supports bigger MTU when compared
to 9216 MTU supported by OcteonTx2 silicon variants. Lookback
interface supports upto 64K and RPM LMAC interfaces support
upto 16K.

This patch does the necessary configuration and adds support
for PF/VF drivers to retrieve max packet size supported via mbox

This patch also configures tx link credit by considering supported
fifo size and max packet length for Octeontx3 silicon.

This patch also removes platform specific name from the driver name.

Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>