tracing: Add ftrace event call parameter to its field descriptor handler

Add the struct ftrace_event_call as a parameter of its show_format()
callback. This way we can use it from the syscall trace events to
retrieve the syscall name from the ftrace event call parameter and
describe its fields using the syscalls metadata.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Jiaying Zhang <jiayingz@google.com>
Cc: Martin Bligh <mbligh@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Jason Baron <jbaron@redhat.com>

include/linux/ftrace_event.h

@@ -116,7 +116,8 @@ struct ftrace_event_call {
 	void			(*unregfunc)(void *);
 	int			id;
 	int			(*raw_init)(void);
-	int			(*show_format)(struct trace_seq *s);
+	int			(*show_format)(struct ftrace_event_call *call,
+					       struct trace_seq *s);
 	int			(*define_fields)(void);
 	struct list_head	fields;
 	int			filter_active;