- Remove explicit clocksource setup and let it be done by OF framework
by defining CLOCKSOURCE_OF_DECLARE() for various timers
- This allows multiple clocksources to be potentially registered
simultaneouly: previously we could only do one - as all of them had
same arc_counter_setup() routine for registration
- Setup routines also ensure that the underlying timer actually exists.
- Remove some of the panic() calls if underlying timer is NOT detcted as
a fallback clocksource might still be available
1. If GRFC doesn't exist, jiffies clocksource gets registered anyways
2. if RTC doesn't exist, TIMER1 cetainly will take over (as it is
always present)
Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>