ftrace: Use BIT() macro

It's cleaner to use the BIT() macro instead of raw shift operation.

Link: http://lkml.kernel.org/r/20191121133815.15040-1-info@metux.net



Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
[ Added BIT() for bits 16 and 17 ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>