ftrace/selftests: Fix spelling mistake "wakeing" -> "waking"

There is a spelling mistake in a trace_printk message. As well as in
the selftests that search for this string.

Link: http://lkml.kernel.org/r/20191115085938.38947-1-colin.king@canonical.com
Link: http://lkml.kernel.org/r/20191115090356.39572-1-colin.king@canonical.com



Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>