octeontx2-af: Remove unnecessary export symbols in CGX driver

Since CGX driver and AF driver are built into a single module
the export symbols in CGX driver are not needed. This patch
gets rid of them.

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