octeontx2-pf: implement transmit schedular allocation algorithm

unlike strict priority, where number of classes are limited to max
8, there is no restriction on the number of dwrr child nodes unless
the count increases the max number of child nodes supported.

Hardware expects strict priority transmit schedular indexes mapped
to their priority. This patch adds defines transmit schedular allocation
algorithm such that the above requirement is honored.

Signed-off-by: Naveen Mamindlapalli <naveenm@marvell.com>
Signed-off-by: Hariprasad Kelam <hkelam@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>