octeontx2-af: Cleanup loopback device checks

PCI device IDs of RVU device IDs are configurable and
RVU PF0's (ie AF's) are currently assumed as VFs that
identify loopback functionality ie LBKVFs. But in some
cases these VFs can be setup for different functionality.
Hence remove assumptions that AF's VFs are always LBK VFs
by renaming 'is_afvf' as 'is_lbkvf' explicitly and also
identify LBK VF using PCI dev ID. Similar change is done
for other VF types.

Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>