x86/hyper-v: include hyperv/ only when CONFIG_HYPERV is set

Code is arch/x86/hyperv/ is only needed when CONFIG_HYPERV is set, the
'basic' support and detection lives in arch/x86/kernel/cpu/mshyperv.c
which is included when CONFIG_HYPERVISOR_GUEST is set.

Signed-off-by: Vitaly Kuznetsov <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Signed-off-by: K. Y. Srinivasan <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

arch/x86/Kbuild

···
 obj-$(CONFIG_XEN) += xen/
 
 # Hyper-V paravirtualization support
-obj-$(CONFIG_HYPERVISOR_GUEST) += hyperv/
+obj-$(subst m,y,$(CONFIG_HYPERV)) += hyperv/
 
 # lguest paravirtualization support
 obj-$(CONFIG_LGUEST_GUEST) += lguest/

arch/x86/include/asm/mshyperv.h

···
 void hyperv_report_panic(struct pt_regs *regs);
 bool hv_is_hypercall_page_setup(void);
 void hyperv_cleanup(void);
-#endif
+#else /* CONFIG_HYPERV */
+static inline void hyperv_init(void) {}
+static inline bool hv_is_hypercall_page_setup(void) { return false; }
+static inline hyperv_cleanup(void) {}
+#endif /* CONFIG_HYPERV */
+
 #ifdef CONFIG_HYPERV_TSCPAGE
 struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
 static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)