clocksource: sunxi: make use of CLKSRC_OF

Using CLKSRC_OF allows to remove the SoC specific sunxi_timer.h header,
and instead of using a custom init function in the machine definition
use the standard clocksource_of_init function.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/arch/arm/mach-sunxi/Kconfig b/arch/arm/mach-sunxi/Kconfig
index 8709a39..06c2894 100644
--- a/arch/arm/mach-sunxi/Kconfig
+++ b/arch/arm/mach-sunxi/Kconfig
@@ -1,6 +1,7 @@
 config ARCH_SUNXI
 	bool "Allwinner A1X SOCs" if ARCH_MULTI_V7
 	select CLKSRC_MMIO
+	select CLKSRC_OF
 	select COMMON_CLK
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_IRQ_CHIP