Chinese: rephrase English introduction in HOWTO

Rephrase the introduction as suggested by Jesper Juhl.
Signed-off-by: Li Yang <leo@zh-kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/zh_CN/HOWTO

 Chinese translated version of Documentation/HOWTO
 
 If you have any comment or update to the content, please contact the
-original document maintainer directly.  However, if you have problem
+original document maintainer directly.  However, if you have a problem
 communicating in English you can also ask the Chinese maintainer for
-help.  Contact the Chinese maintainer, if this translation is outdated
-or there is problem with translation.
+help.  Contact the Chinese maintainer if this translation is outdated
+or if there is a problem with the translation.
 
 Maintainer: Greg Kroah-Hartman <greg@kroah.com>
 Chinese maintainer: Li Yang <leoli@freescale.com>