octeontx2-af: optimize parsing of IPv6 fragments

IPv6 fragmented packet may not contain completed layer 4 information.
So stop KPU parsing after setting ipv6 fragmentation flag.

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