net: Make it easier to parse /proc/net/dev contents.

The contents of /proc/net/dev is annoying to parse, because
it changes whether there is a space after the "ethX:" or not.
It depends upon the size of the "Receive bytes" counter,
if the number is below 7 digits, then there is whitespaces
else if the number is 8 digits or above there is no space
between the ":" and the number.

This patch changes the output to assure there is always a space
between the ":" and the number.  Given that all existing userspace
application already need to handle the whitespaces, I see
no breakage of existing tools.
Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -3206,7 +3206,7 @@ static void dev_seq_printf_stats(struct seq_file *seq, struct net_device *dev)
 {
 	const struct net_device_stats *stats = dev_get_stats(dev);
 
-	seq_printf(seq, "%6s:%8lu %7lu %4lu %4lu %4lu %5lu %10lu %9lu "
+	seq_printf(seq, "%6s: %7lu %7lu %4lu %4lu %4lu %5lu %10lu %9lu "
 		   "%8lu %7lu %4lu %4lu %4lu %5lu %7lu %10lu\n",
 		   dev->name, stats->rx_bytes, stats->rx_packets,
 		   stats->rx_errors,