counter: Refactor main Kconfig file This patch refactors the main Kconfig file in order to align it with the Zephyr code style and to make sure that each Kconfig configuration portion is easily identifiable. Change-Id: Iba83be8ae154df4b29ff423b4c3cc97a78c93e00 Signed-off-by: Vincenzo Frascino <vincenzo.frascino@linaro.org>