Some architectures can optimize local_softirq_pending much better than
softirq_pending(smp_processor_id()), and for all others the former is
just a macro expanding to the later.

Also this is the last use of softirq_pending() in common code, once this
is in we can soon kill the notation of beeing able to query other cpus
softirq pending count.
Signed-off-by: David S. Miller <davem@davemloft.net>