net: prestera: manage matchall and flower priorities

net: prestera: manage matchall and flower priorities

matchall rules can be added only to chain 0 and their priorities have
limitations:
 - new matchall ingress rule's priority must be higher (lower value)
   than any existing flower rule;
 - new matchall egress rule's priority must be lower (higher value)
   than any existing flower rule.

The opposite works for flower rule adding:
 - new flower ingress rule's priority must be lower (higher value)
   than any existing matchall rule;
 - new flower egress rule's priority must be higher (lower value)
   than any existing matchall rule.

This is a hardware limitation and thus must be properly handled in
driver by reporting errors to the user when newly added rule has such a
priority that cannot be installed into the hardware.

To achieve this, the driver must maintain both min/max matchall
priorities for every flower block when user adds/deletes a matchall
rule, as well as both min/max flower priorities for chain 0 for every
adding/deletion of flower rules for chain 0.

Cc: Serhiy Boiko <serhiy.boiko@plvision.eu>
Signed-off-by: Maksym Glubokiy <maksym.glubokiy@plvision.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>