octeontx2-pf: Fix TCP/UDP checksum offload for IPv6 frames

For TCP/UDP checksum offload feature in Octeontx2
expects L3TYPE to be set irrespective of IP header
checksum is being offloaded or not. Currently for
IPv6 frames L3TYPE is not being set resulting in
packet drop with checksum error. This patch fixes
this issue.

Fixes: 3ca6c4c8 ("octeontx2-pf: Add packet transmission support")
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>