xen: Remove Xen PVH/PVHVM dependency on PCI

A Xen PVH domain doesn't have a PCI bus or devices, so it doesn't need
PCI support built in.  Currently, XEN_PVH depends on XEN_PVHVM which
depends on PCI.

Introduce XEN_PVHVM_GUEST as a toplevel item and change XEN_PVHVM to a
hidden variable.  This allows XEN_PVH to depend on XEN_PVHVM without PCI
while XEN_PVHVM_GUEST depends on PCI.

In drivers/xen, compile platform-pci depending on XEN_PVHVM_GUEST since
that pulls in the PCI dependency for linking.
Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20201014175342.152712-2-jandryuk@gmail.comSigned-off-by: Juergen Gross <jgross@suse.com>

arch/x86/xen/Kconfig

@@ -39,16 +39,20 @@ config XEN_DOM0
 	  Support running as a Xen PV Dom0 guest.
 
 config XEN_PVHVM
-	bool "Xen PVHVM guest support"
-	default y
-	depends on XEN && PCI && X86_LOCAL_APIC
-	help
-	  Support running as a Xen PVHVM guest.
+	def_bool y
+	depends on XEN && X86_LOCAL_APIC
 
 config XEN_PVHVM_SMP
 	def_bool y
 	depends on XEN_PVHVM && SMP
 
+config XEN_PVHVM_GUEST
+	bool "Xen PVHVM guest support"
+	default y
+	depends on XEN_PVHVM && PCI
+	help
+	  Support running as a Xen PVHVM guest.
+
 config XEN_512GB
 	bool "Limit Xen pv-domain memory to 512GB"
 	depends on XEN_PV
@@ -76,7 +80,9 @@ config XEN_DEBUG_FS
 	  Enabling this option may incur a significant performance overhead.
 
 config XEN_PVH
-	bool "Support for running as a Xen PVH guest"
+	bool "Xen PVH guest support"
 	depends on XEN && XEN_PVHVM && ACPI
 	select PVH
 	def_bool n
+	help
+	  Support for running as a Xen PVH guest.

drivers/xen/Makefile

@@ -21,7 +21,7 @@ obj-$(CONFIG_XEN_GNTDEV)		+= xen-gntdev.o
 obj-$(CONFIG_XEN_GRANT_DEV_ALLOC)	+= xen-gntalloc.o
 obj-$(CONFIG_XENFS)			+= xenfs/
 obj-$(CONFIG_XEN_SYS_HYPERVISOR)	+= sys-hypervisor.o
-obj-$(CONFIG_XEN_PVHVM)			+= platform-pci.o
+obj-$(CONFIG_XEN_PVHVM_GUEST)		+= platform-pci.o
 obj-$(CONFIG_SWIOTLB_XEN)		+= swiotlb-xen.o
 obj-$(CONFIG_XEN_MCE_LOG)		+= mcelog.o
 obj-$(CONFIG_XEN_PCIDEV_BACKEND)	+= xen-pciback/