sched/preempt, xen: Use need_resched() instead of should_resched()

sched/preempt, xen: Use need_resched() instead of should_resched()

commit 0fa2f5cb2b0ecd8d56baa51f35f09aab234eb0bf upstream.

This code is used only when CONFIG_PREEMPT=n and only in non-atomic context:
xen_in_preemptible_hcall is set only in privcmd_ioctl_hypercall().
Thus preempt_count is zero and should_resched() is equal to need_resched().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Graf <agraf@suse.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150715095201.12246.49283.stgit@buzz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andre Tomt <andre@tomt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>