xen/arm: Fix HAS_PASSTHROUGH selection

HAS_PASSTHROUGH should only be selected on MMU systems. It's been like
that until commit 163c6b5898 added possibility to select HAS_PASSTHROUGH
if PCI_PASSTHROUGH is enabled on Arm64. This is incorrect as it may result
in enabling passthrough/ build on MPU systems. PCI_PASSTHROUGH should
depend on HAS_PASSTHROUGH instead.

Fixes: 163c6b5898 ("xen/arm: pci: introduce PCI_PASSTHROUGH Kconfig option")
Signed-off-by: Michal Orzel <michal.orzel@amd.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/arm/Kconfig

@@ -9,7 +9,6 @@ config ARM_64
 	select 64BIT
 	select HAS_FAST_MULTIPLY
 	select HAS_VPCI_GUEST_SUPPORT if PCI_PASSTHROUGH
-	select HAS_PASSTHROUGH if PCI_PASSTHROUGH
 
 config ARM
 	def_bool y
@@ -263,7 +262,7 @@ source "arch/arm/firmware/Kconfig"
 
 config PCI_PASSTHROUGH
 	bool "PCI passthrough" if EXPERT
-	depends on ARM_64
+	depends on ARM_64 && HAS_PASSTHROUGH
 	help
 	  This option enables PCI device passthrough