proc: Remove empty line in /proc/self/status

If CONFIG_SECCOMP=n, /proc/self/status includes an empty line. This causes
the iotop application to bail out with an error message.

File "/usr/local/lib64/python2.7/site-packages/iotop/data.py", line 196,
	in parse_proc_pid_status
key, value = line.split(':\t', 1)
ValueError: need more than 1 value to unpack

The problem is seen in v4.9.y but not upstream because commit af884cd4a5
("proc: report no_new_privs state") has not been backported to v4.9.y.
The backport of commit fae1fa0fc6 ("proc: Provide details on speculation
flaw mitigations") tried to address the resulting differences but was
wrong, introducing the problem.

Fixes: 51ef9af2a3 ("proc: Provide details on speculation flaw mitigations")
Cc: Kees Cook <keescook@chromium.org>
Cc: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Kees Cook <keescook@chromium.org>

fs/proc/array.c

@@ -346,8 +346,9 @@ static inline void task_seccomp(struct seq_file *m, struct task_struct *p)
 {
 #ifdef CONFIG_SECCOMP
 	seq_put_decimal_ull(m, "Seccomp:\t", p->seccomp.mode);
+	seq_putc(m, '\n');
 #endif
-	seq_printf(m, "\nSpeculation_Store_Bypass:\t");
+	seq_printf(m, "Speculation_Store_Bypass:\t");
 	switch (arch_prctl_spec_ctrl_get(p, PR_SPEC_STORE_BYPASS)) {
 	case -EINVAL:
 		seq_printf(m, "unknown");