net/sched: add block pointer to tc_cls_common_offload structure

Some actions like the police action are stateful and could share state
between devices. This is incompatible with offloading to multiple devices
and drivers might want to test for shared blocks when offloading.
Store a pointer to the tcf_block structure in the tc_cls_common_offload
structure to allow drivers to determine when offloads apply to a shared
block.

Signed-off-by: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>