tracing: Remove syscall_exit_fields

There is no need for syscall_exit_fields as the syscall
exit event class can already host the fields in its structure,
like most other trace events do by default. Use that
default behavior instead.

Following this scheme, we don't need anymore to override the
get_fields() callback of the syscall exit event class either.

Hence both syscall_exit_fields and syscall_get_exit_fields() can
be removed.

Also changed some indentation to keep the following under 80
characters:

".fields		= LIST_HEAD_INIT(event_class_syscall_exit.fields),"

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <4D301C0E.8090408@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>