Revert "proc/base: make prompt shell start from new line after executing "cat /proc/$pid/wchan""

This reverts the 4.6-rc1 commit 7e2bc81 ("proc/base: make prompt
shell start from new line after executing "cat /proc/$pid/wchan")
because it breaks /proc/$PID/whcan formatting in ps and top.

Revert also because the patch is inconsistent - it adds a newline at the
end of only the '0' wchan, and does not add a newline when
/proc/$PID/wchan contains a symbol name.

eg.
$ ps -eo pid,stat,wchan,comm
PID STAT WCHAN  COMMAND
...
1189 S    -      dbus-launch
1190 Ssl  0
dbus-daemon
1198 Sl   0
lightdm
1299 Ss   ep_pol systemd
1301 S    -      (sd-pam)
1304 Ss   wait   sh

Signed-off-by: Robin Humble <[email protected]>
Cc: Minfei Huang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: plaguedbypenguins

fs/proc/base.c

@@ -434,7 +434,7 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
 			&& !lookup_symbol_name(wchan, symname))
 		seq_printf(m, "%s", symname);
 	else
-		seq_puts(m, "0\n");
+		seq_putc(m, '0');
 
 	return 0;
 }