In order to increase the compilation test coverage, add the COMPILE_TEST
so the driver can be compiled even if it does not belong to the platform
or the architecture.

The io.h header inclusion is also added as it the driver does not compile
on UM platform.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

All the clocksource drivers's init function are now converted to return
an error code. CLOCKSOURCE_OF_DECLARE is no longer used as well as the
clksrc-of table.

Let's convert back the names:
 - CLOCKSOURCE_OF_DECLARE_RET => CLOCKSOURCE_OF_DECLARE
 - clksrc-of-ret              => clksrc-of

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

For exynos_mct and samsung_pwm_timer:
Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>

For arch/arc:
Acked-by: Vineet Gupta <vgupta@synopsys.com>

For mediatek driver:
Acked-by: Matthias Brugger <matthias.bgg@gmail.com>

For the Rockchip-part
Acked-by: Heiko Stuebner <heiko@sntech.de>

For STi :
Acked-by: Patrice Chotard <patrice.chotard@st.com>

For the mps2-timer.c and versatile.c changes:
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>

For the OXNAS part :
Acked-by: Neil Armstrong <narmstrong@baylibre.com>

For LPC32xx driver:
Acked-by: Sylvain Lemieux <slemieux.tyco@gmail.com>

For Broadcom Kona timer change:
Acked-by: Ray Jui <ray.jui@broadcom.com>

For Sun4i and Sun5i:
Acked-by: Chen-Yu Tsai <wens@csie.org>

For Meson6:
Acked-by: Carlo Caione <carlo@caione.org>

For Keystone:
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>

For NPS:
Acked-by: Noam Camus <noamca@mellanox.com>

For bcm2835:
Acked-by: Eric Anholt <eric@anholt.net>

The init functions do not return any error. They behave as the following:

 - panic, thus leading to a kernel crash while another timer may work and
   make the system boot up correctly

 or

 - print an error and let the caller unaware if the state of the system

Change that by converting the init functions to return an error conforming
to the CLOCKSOURCE_OF_RET prototype.

Proper error handling (rollback, errno value) will be changed later case
by case, thus this change just return back an error or success in the init
function.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Maxime Coquelin <maxime.coquelin@st.com>

This patch adds clocksource support for ARMv7-M's System timer,
also known as SysTick.

Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>