octeontx2-af: add parser support for Forward DSA

Marvell Prestera switches supports distributed switch architecture
by inserting Forward DSA tag of 4 bytes right after ethernet SMAC.
This tag don't have a tpid field.

This patch provides parser and extraction support for the same.
Default ldata extraction profile added for FDSA such that Src_port
is extracted and placed inplace of vlanid field. Like extended DSA
and eDSA tags,a special PKIND of 62 is used for this tag.

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