package/rapidxml: fix 'usability' typo in help text

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
(cherry picked from commit d21e6f815df3a1814b752b9b48c99b13903f3239)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/rapidxml/Config.in

@@ -2,7 +2,7 @@ config BR2_PACKAGE_RAPIDXML
 	bool "rapidxml"
 	help
 	  RapidXml is an attempt to create the fastest XML parser
-	  possible, while retaining useability, portability and
+	  possible, while retaining usability, portability and
 	  reasonable W3C compatibility. It is an in-situ parser with
 	  parsing speed approaching speed of strlen function executed
 	  on the same data.