kstrtox: Drop extern keyword in the simple_strtox() declarations

kstrtox: Drop extern keyword in the simple_strtox() declarations

There is legacy 'extern' keyword for the exported simple_strtox()
function which are the artefact that can be removed. So drop it.

While at it, tweak the declaration to provide parameter names.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20260331070519.5974-7-ddiss@suse.de
Reviewed-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>