octeontx2-af: Optimize KPU1 processing for variable-length headers

Optimized KPU1 entry processing for variable-length custom L2 headers
of size 24B, 90B by
	- Moving LA LTYPE parsing for 24B and 90B headers to PKIND.
	- Removing LA flags assignment for 24B and 90B headers.
	- Reserving a PKIND 55 to parse variable length headers.

Also, new mailbox(NPC_SET_PKIND) added to configure PKIND with
corresponding variable-length offset, mask, and shift count
(NPC_AF_KPUX_ENTRYX_ACTION0).

Signed-off-by: Kiran Kumar K <kirankumark@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>