sparse doc: fix reference path

Documentation/sparse.txt has been moved to
Documentation/dev-tools/sparse.rst

Signed-off-by: Cao jin <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/translations/zh_CN/sparse.txt

···
-Chinese translated version of Documentation/sparse.txt
+Chinese translated version of Documentation/dev-tools/sparse.rst
 
 If you have any comment or update to the content, please contact the
 original document maintainer directly.  However, if you have a problem
···
 
 Chinese maintainer: Li Yang <[e-mail]>
 ---------------------------------------------------------------------
-Documentation/sparse.txt 的中文翻译
+Documentation/dev-tools/sparse.rst 的中文翻译
 
 如果想评论或更新本文的内容，请直接联系原文档的维护者。如果你使用英文
 交流有困难的话，也可以向中文版维护者求助。如果本翻译更新不及时或者翻

Makefile

···
 # Use 'make C=2' to enable checking of *all* source files, regardless
 # of whether they are re-compiled or not.
 #
-# See the file "Documentation/sparse.txt" for more details, including
-# where to get the "sparse" utility.
+# See the file "Documentation/dev-tools/sparse.rst" for more details,
+# including where to get the "sparse" utility.
 
 ifeq ("$(origin C)", "command line")
   KBUILD_CHECKSRC = $(C)