octeontx2-af: print error message incase of invalid pf mapping

During AF driver initialization, it creates a mapping between pf to
cgx,lmac pair. Whenever there is a physical link change, using this
mapping driver forwards the message to the associated netdev.

This patch prints error message incase of cgx,lmac pair is not
associated with any pf netdev.

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