lib/string_choices: Add str_up_down() helper

Add str_up_down() helper to return "up" or "down" string literal.
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20240725101841.574-1-michal.wajdeczko@intel.comSigned-off-by: Kees Cook <kees@kernel.org>

include/linux/string_choices.h

@@ -42,6 +42,11 @@ static inline const char *str_yes_no(bool v)
 	return v ? "yes" : "no";
 }
 
+static inline const char *str_up_down(bool v)
+{
+	return v ? "up" : "down";
+}
+
 /**
  * str_plural - Return the simple pluralization based on English counts
  * @num: Number used for deciding pluralization