tracing: move tgid out of generic entry and into userstack

The userstack trace required the recording of the tgid entry.
Unfortunately, it was added to the generic entry where it wasted
4 bytes of every entry and was only used by one entry.

This patch moves it out of the generic field and moves it into the
only user (userstack_entry).

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index acaa680..b69697b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -101,6 +101,7 @@
 
 struct userstack_entry {
 	struct trace_entry	ent;
+	unsigned int		tgid;
 	unsigned long		caller[FTRACE_STACK_ENTRIES];
 };