sched, sh: Fold finish_arch_switch() into switch_to()

sched, sh: Fold finish_arch_switch() into switch_to()

The code looks buggy; why would we be restoring the previous task's
DSP state after we've switched to the next task?

Fix that and put the restore in switch_to(), removing the need for
finish_arch_switch().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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
Cc: michael@amarulasolutions.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>