kunit/usercopy: Add missing MODULE_DESCRIPTION()

Fix warning seen with:

$ make allmodconfig && make W=1 C=1 lib/usercopy_kunit.ko
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/usercopy_kunit.o
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kees Cook <kees@kernel.org>
Reviewed-by: Rae Moar <rmoar@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

lib/usercopy_kunit.c

@@ -331,4 +331,5 @@ static struct kunit_suite usercopy_test_suite = {
 
 kunit_test_suites(&usercopy_test_suite);
 MODULE_AUTHOR("Kees Cook <kees@kernel.org>");
+MODULE_DESCRIPTION("Kernel module for testing copy_to/from_user infrastructure");
 MODULE_LICENSE("GPL");