net: proc: fix build failed when procfs is not configured

net: proc: fix build failed when procfs is not configured

commit 8c8be203143f49828d16f754ee62c85c8b9e4c3c
"net: proc: change proc_net_fops_create to proc_create"
uses proc_create to replace proc_net_fops_create, when
CONFIG_PROC isn't configured, some build error will
occurs.

net/packet/af_packet.c: In function 'packet_net_init':
net/packet/af_packet.c:3831:48: error: 'packet_seq_fops' undeclared (first use in this function)
net/packet/af_packet.c:3831:48: note: each undeclared identifier is reported only once for each function it appears in

There may be other build fails like above,this patch
change proc_create from function to macros when CONFIG_PROC
is not configured,just like what proc_net_fops_create did
before this commit.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>