x86/xen: Move pv irq related functions under CONFIG_XEN_PV umbrella

All functions in arch/x86/xen/irq.c and arch/x86/xen/xen-asm*.S are
specific to PV guests. Include them in the kernel with CONFIG_XEN_PV only.

Make the PV specific code in arch/x86/entry/entry_*.S dependent on
CONFIG_XEN_PV instead of CONFIG_XEN.

The HVM specific code should depend on CONFIG_XEN_PVHVM.

While at it reformat the Makefile to make it more readable.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel@lists.xenproject.org
Cc: virtualization@lists.linux-foundation.org
Cc: akataria@vmware.com
Cc: rusty@rustcorp.com.au
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/20180828074026.820-2-jgross@suse.com

arch/x86/entry/entry_64.S

@@ -1050,7 +1050,7 @@ ENTRY(do_softirq_own_stack)
 	ret
 ENDPROC(do_softirq_own_stack)
 
-#ifdef CONFIG_XEN
+#ifdef CONFIG_XEN_PV
 idtentry hypervisor_callback xen_do_hypervisor_callback has_error_code=0
 
 /*
@@ -1130,11 +1130,13 @@ ENTRY(xen_failsafe_callback)
 	ENCODE_FRAME_POINTER
 	jmp	error_exit
 END(xen_failsafe_callback)
+#endif /* CONFIG_XEN_PV */
 
+#ifdef CONFIG_XEN_PVHVM
 apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
 	xen_hvm_callback_vector xen_evtchn_do_upcall
+#endif
 
-#endif /* CONFIG_XEN */
 
 #if IS_ENABLED(CONFIG_HYPERV)
 apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
@@ -1151,7 +1153,7 @@ idtentry debug			do_debug		has_error_code=0	paranoid=1 shift_ist=DEBUG_STACK
 idtentry int3			do_int3			has_error_code=0
 idtentry stack_segment		do_stack_segment	has_error_code=1
 
-#ifdef CONFIG_XEN
+#ifdef CONFIG_XEN_PV
 idtentry xennmi			do_nmi			has_error_code=0
 idtentry xendebug		do_debug		has_error_code=0
 idtentry xenint3		do_int3			has_error_code=0