[S390] s390: Fix build for !CONFIG_S390_GUEST + CONFIG_VIRTIO_CONSOLE

The s390 kernel does not compile if virtio console is enabled, but guest
support is disabled:

LD .tmp_vmlinux1
arch/s390/kernel/built-in.o: In function `setup_arch':
/space/linux-2.5/arch/s390/kernel/setup.c:773: undefined reference to
`s390_virtio_console_init'

The fix is related to
commit 99e65c92f2bbf84f43766a8bf701e36817d62822
Author: Christian Borntraeger <[e-mail]>
Date: Fri Jul 25 15:50:04 2008 +0200
KVM: s390: Fix guest kconfig

Which changed the build process to build kvm_virtio.c only if CONFIG_S390_GUEST
is set. We must ifdef the prototype in the header file accordingly.

Reported-by: Heiko Carstens <[e-mail]>
Signed-off-by: Christian Borntraeger <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/include/asm/kvm_virtio.h

···
 
 #ifdef __KERNEL__
 /* early virtio console setup */
-#ifdef CONFIG_VIRTIO_CONSOLE
+#ifdef CONFIG_S390_GUEST
 extern void s390_virtio_console_init(void);
 #else
 static inline void s390_virtio_console_init(void)