9p: fix memleak in fs/9p/v9fs.c

This patch fixes a memory leak introduced by
commit ba17674f.

Spotted by the Coverity checker.
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

fs/9p/v9fs.c

@@ -162,6 +162,7 @@ static void v9fs_parse_options(struct v9fs_session_info *v9ses)
 				if (*e != '\0')
 					v9ses->uid = ~0;
 			}
+			kfree(s);
 			break;
 
 		default: