ARM: imx: move timer driver into drivers/clocksource

After the cleanup on imx timer driver, now it's ready to be moved into
drivers/clocksource/.  Let's do it.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --cc arch/arm/mach-imx/Kconfig
Simple merge

diff --cc arch/arm/mach-imx/Makefile
Simple merge

diff --cc drivers/clocksource/Kconfig
Simple merge

diff --cc drivers/clocksource/Makefile
Simple merge

diff --cc drivers/clocksource/timer-imx-gpt.c
Simple merge