tools/counter: Create Counter tools

This creates an example Counter program under tools/counter/*
to exemplify the Counter character device interface.

Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/7c0f975ba098952122302d258ec9ffdef04befaf.1632884256.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>