s390/uv: export prot_virt_guest symbol in uv

The inline function is_prot_virt_guest() in asm/uv.h makes use of the
prot_virt_guest symbol. As this inline function can be called by other
parts of the kernel (modules and built-in), the symbol should be
exported, similar to the prot_virt_host symbol.

One consumer of is_prot_virt_guest() will be the ap bus code.

Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Holger Dengler <dengler@linux.ibm.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/kernel/uv.c

@@ -21,6 +21,7 @@
 /* the bootdata_preserved fields come from ones in arch/s390/boot/uv.c */
 #ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
 int __bootdata_preserved(prot_virt_guest);
+EXPORT_SYMBOL(prot_virt_guest);
 #endif
 
 /*