net: ethernet: ti: Add desc_infos member to struct k3_cppi_desc_pool

This patch introduces a member and the related accessors which can be
used to store descriptor specific additional information. This member
can store, for instance, an ID to differentiate a skb TX buffer type
from a xdpf TX buffer type.

Signed-off-by: Julien Panis <jpanis@baylibre.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>