ARM: convert arm/arm64 arch timer to use CLKSRC_OF init

This converts arm and arm64 to use CLKSRC_OF DT based initialization for
the arch timer. A new function arch_timer_arch_init is added to allow for
arch specific setup.

This has a side effect of enabling sched_clock on omap5 and exynos5. There
should not be any reason not to use the arch timers for sched_clock.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Simon Horman <horms@verge.net.au>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-omap@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>

arch/arm/mach-omap2/timer.c

@@ -46,7 +46,6 @@
 #include <asm/smp_twd.h>
 #include <asm/sched_clock.h>
 
-#include <asm/arch_timer.h>
 #include "omap_hwmod.h"
 #include "omap_device.h"
 #include <plat/counter-32k.h>
@@ -624,9 +623,7 @@ void __init omap5_realtime_timer_init(void)
 	omap5_sync32k_timer_init();
 	realtime_counter_init();
 
-	err = arch_timer_of_register();
-	if (err)
-		pr_err("%s: arch_timer_register failed %d\n", __func__, err);
+        clocksource_of_init();
 }
 #endif /* CONFIG_SOC_OMAP5 */