x86/entry: Rename ___preempt_schedule

Because moar '_' isn't always moar readable.

git grep -l "___preempt_schedule\(_notrace\)*" | while read file;
do
	sed -ie 's/___preempt_schedule\(_notrace\)*/preempt_schedule\1_thunk/g' $file;
done

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20200320115858.995685950@infradead.org