[PATCH] [AX25] fix lack of /proc/net/ax25 labels header

[PATCH]  [AX25] fix lack of /proc/net/ax25 labels header

/pro/net/ax25 never had a chance to be displayed in easily
understandable format.

First reason was the absence of labels header, second reason was
pourly formated proc/net/ax25 lines.

Actually ax25_info_start() did not return SEQ_START_TOKEN and there was 
no test for displaying header in ax25_info_show().

Another reason for lack of readability was poorly formatted 
/proc/net/ax25 as shown:

00000000fb21b658 ax0 F6BVP-12 * 0 0 0 0 0 10 0 3 0 300 0 0 0 10 5 2 256 
0 0 14949

The proposed patch initializes SEQ_START_TOKEN in ax25_list_start and 
add a test for first time displaying header in ax25_info_show().

In addition this patch provides a better formated display of /proc/net/
ax25 aka /proc/net/nr or /proc/net/rose

magic            dev src_addr  dest_addr digi1     digi2 .. st vs vr va 
    t1     t2      t3     idle    n2   rtt window  paclen Snd-Q Rcv-Q  inode
0000000040471056 ax0 F6BVP-13  F6BVP-9   -         -         3  5  4  5 
   0/03   0/3   189/300   0/0    0/10    1   2      256    *     *     *
000000002f11c115 ax0 F6BVP-13  F6BVP-11  -         -         3  5  4  5 
   0/06   0/3   155/300   0/0    0/10    3   2      256    *     *     *
00000000c534288b ax0 F6BVP-12  *         -         -         0  0  0  0 
   0/10   0/3     0/300   0/0    0/10    5   2      256    0     0     50994


Signed-off-by: Bernard Pidoux <redacted>