locking/lockdep: Fix string sizing bug that triggers a format-truncation compiler-warning

On an allyesconfig, with "treat warnings as errors" unset, GCC emits
these warnings:

	kernel/locking/lockdep_proc.c:438:32: Warning: Format specifier '%lld' may
		be truncated when writing 1 to 17 bytes into a region
		of size 15 [-Wformat-truncation=]

	kernel/locking/lockdep_proc.c:438:31: Note: Format directive argument is
		in the range [-9223372036854775, 9223372036854775]

	kernel/locking/lockdep_proc.c:438:9: Note: 'snprintf' has output
		between 5 and 22 bytes into a target of size 15

In seq_time(), the longest s64 is "-9223372036854775808"-ish, which
converted to the fixed-point float format is "-9223372036854775.80": 21 bytes,
plus termination is another byte: 22. Therefore, a larger buffer size
of 22 is needed here - not 15. The code was safe due to the snprintf().

Fix it.

Signed-off-by: Lucy Mielke <lucymielke@icloud.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/ZSfOEHRkZAWaQr3U@fedora.fritz.box

kernel/locking/lockdep_proc.c

@@ -440,7 +440,7 @@ static void snprint_time(char *buf, size_t bufsiz, s64 nr)
 
 static void seq_time(struct seq_file *m, s64 time)
 {
-	char num[15];
+	char num[22];
 
 	snprint_time(num, sizeof(num), time);
 	seq_printf(m, " %14s", num);