phonet: fix compilation with gcc-3.4

  CC [M]  net/phonet/af_phonet.o
net/phonet/af_phonet.c: In function `pn_socket_create':
net/phonet/af_phonet.c:38: sorry, unimplemented: inlining failed in call to 'phonet_proto_put': function body not available
net/phonet/af_phonet.c:99: sorry, unimplemented: called from here
make[3]: *** [net/phonet/af_phonet.o] Error 1

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>