Revert "KVM: allow host header to be included even for !CONFIG_KVM"

This reverts commit f445f11eb2cc265dd47da5b2e864df46cd6e5a82 as
it breaks PPC with CONFIG_KVM=n.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

include/linux/kvm_host.h

@@ -1,8 +1,6 @@
 #ifndef __KVM_HOST_H
 #define __KVM_HOST_H
 
-#if IS_ENABLED(CONFIG_KVM)
-
 /*
  * This work is licensed under the terms of the GNU GPL, version 2.  See
  * the COPYING file in the top-level directory.
@@ -1057,8 +1055,5 @@ static inline bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu)
 }
 
 #endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
-#else
-static inline void __guest_enter(void) { return; }
-static inline void __guest_exit(void) { return; }
-#endif /* IS_ENABLED(CONFIG_KVM) */
 #endif
+