bpf: Use bpf global token instead mplock to protect bpf stuffs

bpf: Use bpf global token instead mplock to protect bpf stuffs

Submitted-by: tuxillo@ w/ modification

• [DBH] sys/dev/netif/ic/if_ic.c
• [DBH] sys/dev/netif/plip/if_plip.c
• [DBH] sys/net/bpf.c
• [DBH] sys/net/bpf.h
• [DBH] sys/net/disc/if_disc.c
• [DBH] sys/net/ef/if_ef.c
• [DBH] sys/net/ethernet.h
• [DBH] sys/net/faith/if_faith.c
• [DBH] sys/net/gif/if_gif.c
• [DBH] sys/net/gre/if_gre.c
• [DBH] sys/net/if_loop.c
• [DBH] sys/net/pf/if_pflog.c
• [DBH] sys/net/pf/if_pfsync.c
• [DBH] sys/net/sl/if_sl.c
• [DBH] sys/net/stf/if_stf.c
• [DBH] sys/net/tun/if_tun.c
• [DBH] sys/netgraph/fec/ng_fec.c
• [DBH] sys/netgraph/iface/ng_iface.c
• [DBH] sys/netgraph7/iface/ng_iface.c
• [DBH] sys/netinet/ip_gre.c
• [DBH] sys/netproto/802_11/wlan/ieee80211_radiotap.c