counter: Cleanup lingering atomic.h includes

With the removal of the chrdev_lock atomic flag, the counter-sysfs.c and
counter-chrdev.c no longer needs to include the atomic.h header file.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/20211021103514.955622-1-vilhelm.gray@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>