lib/test_rhashtable: add missing MODULE_DESCRIPTION() macro

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in lib/test_rhashtable.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240531-md-lib-test_rhashtable-v1-1-cd6d4138f1b6@quicinc.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

lib/test_rhashtable.c

@@ -811,4 +811,5 @@ static void __exit test_rht_exit(void)
 module_init(test_rht_init);
 module_exit(test_rht_exit);
 
+MODULE_DESCRIPTION("Resizable, Scalable, Concurrent Hash Table test module");
 MODULE_LICENSE("GPL v2");