net: add napi_if_scheduled_mark_missed

The function napi_if_scheduled_mark_missed is used to check if the
NAPI context is scheduled, if so set NAPIF_STATE_MISSED and return
true. Used by the AF_XDP zero-copy i40e Tx code implementation in
order to make sure that irq affinity is honored by the napi context.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>