net: optimize napi_schedule_rps()

net: optimize napi_schedule_rps()

Based on initial patch from Jason Xing.

Idea is to not raise NET_RX_SOFTIRQ from napi_schedule_rps()
when we queued a packet into another cpu backlog.

We can do this only in the context of us being called indirectly
from net_rx_action(), to have the guarantee our rps_ipi_list
will be processed before we exit from net_rx_action().

Link: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Eric Dumazet <[email protected]>
Cc: Jason Xing <[email protected]>
Reviewed-by: Jason Xing <[email protected]>
Tested-by: Jason Xing <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>