lib/test_lockup.c: make test_inode static

Fix the following sparse warning:

  lib/test_lockup.c:145:14: warning: symbol 'test_inode' was not declared.
  Should it be static?
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200417074021.46411-1-yanaijie@huawei.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/test_lockup.c

@@ -142,7 +142,7 @@ module_param(reallocate_pages, bool, 0400);
 MODULE_PARM_DESC(reallocate_pages, "free and allocate pages between iterations");
 
 struct file *test_file;
-struct inode *test_inode;
+static struct inode *test_inode;
 static char test_file_path[256];
 module_param_string(file_path, test_file_path, sizeof(test_file_path), 0400);
 MODULE_PARM_DESC(file_path, "file path to test");