docs: counter: Fix spelling

"Miscellaneous" is the correct spelling.

Reviewed-by: David Lechner <david@lechnology.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/880c2fd0e2e91b8962c9d388b37ba582d548db8e.1623201081.git.vilhelm.gray@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>