lib/vsprintf: declare no_hash_pointers in sprintf.h

Sparse is not happy to see non-static variable without declaration:
lib/vsprintf.c:61:6: warning: symbol 'no_hash_pointers' was not declared.
Should it be static?

Declare respective variable in the sprintf.h. With this, add a comment to
discourage its use if no real need.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Andy Shevchenko <[e-mail]>
Acked-by: Marco Elver <[e-mail]>
Reviewed-by: Petr Mladek <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: Rasmus Villemoes <[e-mail]>
Cc: Sergey Senozhatsky <[e-mail]>
Cc: Steven Rostedt (Google) <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/linux/sprintf.h

···
 __scanf(2, 3) int sscanf(const char *, const char *, ...);
 __scanf(2, 0) int vsscanf(const char *, const char *, va_list);
 
+/* These are for specific cases, do not use without real need */
+extern bool no_hash_pointers;
 int no_hash_pointers_enable(char *str);
 
 #endif	/* _LINUX_KERNEL_SPRINTF_H */

lib/test_printf.c

···
 static char *test_buffer __initdata;
 static char *alloced_buffer __initdata;
 
-extern bool no_hash_pointers;
-
 static int __printf(4, 0) __init
 do_test(int bufsize, const char *expect, int elen,
 	const char *fmt, va_list ap)

mm/kfence/report.c

···
 #include <linux/printk.h>
 #include <linux/sched/debug.h>
 #include <linux/seq_file.h>
+#include <linux/sprintf.h>
 #include <linux/stacktrace.h>
 #include <linux/string.h>
 #include <trace/events/error_report.h>
···
 #ifndef ARCH_FUNC_PREFIX
 #define ARCH_FUNC_PREFIX ""
 #endif
-
-extern bool no_hash_pointers;
 
 /* Helper function to either print to a seq_file or to console. */
 __printf(2, 3)