octeontx2-af: fix issue with IPv6 ext match for RSS

While performing RSS based on IPv6, extension ltype
is not being considered. This will be problem for
fragmented packets or packets with extension header.
Adding changes to match IPv6 ext header along with IPv6
ltype.

Fixes: 41a7aa7b

 ("octeontx2-af: NIX Rx flowkey configuration for RSS")
Signed-off-by: Kiran Kumar K <kirankumark@marvell.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>