vsprintf: Only export no_hash_pointers to test module

vsprintf: Only export no_hash_pointers to test module

Aside from the printf test module, no module should ever use this symbol.

Suggested-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/all/aWpwMyFEfpCNN297@pathway.suse.cz/
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/all/aW3em-KplLVofU5z@smile.fi.intel.com/
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/20260504-restricted-pointers-kunit-test-v2-1-19e8b1c0fbeb@linutronix.de
[pmladek@suse.com: Removed questionable ifdeffery.]
Signed-off-by: Petr Mladek <pmladek@suse.com>