avr32: Generic clockevents support

This combines three patches from David Brownell:
  * avr32: tclib support
  * avr32: simplify clocksources
  * avr32: Turn count/compare into a oneshot clockevent device

Register both TC blocks (instead of just the first one) so that
the AT32/AT91 tclib code will pick them up (instead of just the
avr32-only PIT-style clocksource).

Rename the first one and its resources appropriately.

More cleanups to the cycle counter clocksource code

 - Disable all the weak symbol magic; remove the AVR32-only TCB-based
   clocksource code (source and header).

 - Mark the __init code properly.

 - Don't forget to report IRQF_TIMER.

 - Make the system work properly with this clocksource, by preventing
   use of the CPU "idle" sleep state in the idle loop when it's used.

Package the avr32 count/compare timekeeping support as a oneshot
clockevent device, so it supports NO_HZ and high res timers.
This means it also supports plugging in other clockevent devices
and clocksources.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>