log: Fix incorect range check in log_get_cat_name()

This allows access to an element after the end of the array. Fix it.

Reported-by: Coverity (CID: 173279)
Signed-off-by: Simon Glass <sjg@chromium.org>

include/log.h

@@ -274,7 +274,8 @@ struct log_filter {
  * log_get_cat_name() - Get the name of a category
  *
  * @cat: Category to look up
- * @return category name (which may be a uclass driver name)
+ * @return category name (which may be a uclass driver name) if found, or
+ *	 "<invalid>" if invalid, or "<missing>" if not found
  */
 const char *log_get_cat_name(enum log_category_t cat);