liquidio: update VF's netdev->max_mtu if there's a change in PF's MTU

A VF's MTU is capped at the parent PF's MTU.  So if there's a change in the
PF's MTU, then update the VF's netdev->max_mtu.

Also remove duplicate log messages for MTU change.

Signed-off-by: Veerasenareddy Burru <veerasenareddy.burru@cavium.com>
Signed-off-by: Raghu Vatsavayi <raghu.vatsavayi@cavium.com>
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>