tools lib traceevent: Handle trace_printk() "%px"

With security updates, %p in the kernel is hashed to protect true kernel
locations. But trace_printk() is not allowed in production systems, and
when a pointer is used, there are many times that the actual address is
needed. "%px" produces the real address. But libtraceevent does not know how
to handle that extension. Add it.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tzvetomir Stoyanov <tstoyanov@vmware.com>
Link: http://lkml.kernel.org/r/20190401164342.837312153@goodmis.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/event-parse.c

@@ -4338,6 +4338,7 @@ static struct tep_print_arg *make_bprint_args(char *fmt, void *data, int size, s
 					case 'S':
 					case 'f':
 					case 'F':
+					case 'x':
 						break;
 					default:
 						/*