tracing/signal: Use explicit conversion instead of vague downcast

The trace event framework, at this point, lacks support for capabilities
as there is no way to properly output those when logging events,
and casting a user pointer to a type that cannot actually
hold a CHERI capability brings its own issues, so, for the time being,
use user_ptr_addr to extract the address from a user pointer of interest.
Tested-by: Zachary Leaf <zachary.leaf@arm.com>
Signed-off-by: Beata Michalska <beata.michalska@arm.com>

include/trace/events/signal.h

@@ -103,14 +103,14 @@ TRACE_EVENT(signal_deliver,
 		__field(	int,		sig		)
 		__field(	int,		errno		)
 		__field(	int,		code		)
-		__field(	unsigned long,	sa_handler	)
+		__field(	ptraddr_t,	sa_handler	)
 		__field(	unsigned long,	sa_flags	)
 	),
 
 	TP_fast_assign(
 		__entry->sig	= sig;
 		TP_STORE_SIGINFO(__entry, info);
-		__entry->sa_handler	= (unsigned long)ka->sa.sa_handler;
+		__entry->sa_handler	= user_ptr_addr(ka->sa.sa_handler);
 		__entry->sa_flags	= ka->sa.sa_flags;
 	),