um: harddog: add missing MODULE_DESCRIPTION() macro

With ARCH=um, make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in arch/um/drivers/harddog.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://patch.msgid.link/20240702-md-um-arch-um-drivers-v1-1-79e4f50b5bab@quicinc.comSigned-off-by: Johannes Berg <johannes.berg@intel.com>

arch/um/drivers/harddog_kern.c

@@ -49,6 +49,7 @@
 #include "mconsole.h"
 #include "harddog.h"
 
+MODULE_DESCRIPTION("UML hardware watchdog");
 MODULE_LICENSE("GPL");
 
 static DEFINE_MUTEX(harddog_mutex);