sched, avr32: Remove finish_arch_switch()

Fold the tracing hook into switch_to() in order to remove
finish_arch_switch().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Hans-Christian Egtvedt <egtvedt@samfundet.no>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>