KVM: remove unused guest_enter

After commit 61bd0f66 ("KVM: PPC: Book3S HV: Fix guest time accounting
with VIRT_CPU_ACCOUNTING_GEN"), no one use this function anymore, So better
to remove it.
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/linux/context_tracking.h

@@ -154,15 +154,6 @@ static inline void guest_exit_irqoff(void)
 }
 #endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */
 
-static inline void guest_enter(void)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	guest_enter_irqoff();
-	local_irq_restore(flags);
-}
-
 static inline void guest_exit(void)
 {
 	unsigned long flags;