net: filter: split filter.c into two files

BPF is used in several kernel components. This split creates logical boundary
between generic eBPF core and the rest

kernel/bpf/core.c: eBPF interpreter

net/core/filter.c: classic->eBPF converter, classic verifiers, socket filters

This patch only moves functions.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/Makefile

@@ -87,6 +87,7 @@ obj-$(CONFIG_RING_BUFFER) += trace/
 obj-$(CONFIG_TRACEPOINTS) += trace/
 obj-$(CONFIG_IRQ_WORK) += irq_work.o
 obj-$(CONFIG_CPU_PM) += cpu_pm.o
+obj-$(CONFIG_NET) += bpf/
 
 obj-$(CONFIG_PERF_EVENTS) += events/
 

kernel/bpf/Makefile

+obj-y := core.o