xen64: fix !HVC_XEN build dependency

fix:

arch/x86/xen/built-in.o: In function `set_page_prot':
enlighten.c:(.text+0x111d): undefined reference to `xen_raw_printk'
arch/x86/xen/built-in.o: In function `xen_start_kernel':
: undefined reference to `xen_raw_console_write'
arch/x86/xen/built-in.o: In function `xen_start_kernel':
: undefined reference to `xen_raw_console_write'
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/xen/hvc-console.h

@@ -5,11 +5,12 @@ extern struct console xenboot_console;
 
 #ifdef CONFIG_HVC_XEN
 void xen_console_resume(void);
+void xen_raw_console_write(const char *str);
+void xen_raw_printk(const char *fmt, ...);
 #else
 static inline void xen_console_resume(void) { }
+static inline void xen_raw_console_write(const char *str) { }
+static inline void xen_raw_printk(const char *fmt, ...) { }
 #endif
 
-void xen_raw_console_write(const char *str);
-void xen_raw_printk(const char *fmt, ...);
-
 #endif	/* XEN_HVC_CONSOLE_H */