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>

arch/arm/mach-imx/Makefile

@@ -1,4 +1,4 @@
-obj-y := time.o cpu.o system.o irq-common.o
+obj-y := cpu.o system.o irq-common.o
 
 obj-$(CONFIG_SOC_IMX1) += mm-imx1.o
 obj-$(CONFIG_SOC_IMX21) += mm-imx21.o