arm: don't build core parking code

It's wired up on x86 only.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/Rules.mk
+++ b/xen/arch/x86/Rules.mk
@@ -13,6 +13,7 @@ HAS_EHCI := y
 HAS_KEXEC := y
 HAS_GDBSX := y
 HAS_PDX := y
+HAS_CORE_PARKING := y
 xenoprof := y
 
 CFLAGS += -I$(BASEDIR)/include 
--- b/xen/common/Makefile
+++ a/xen/common/Makefile
@@ -1,5 +1,5 @@
 obj-y += bitmap.o
-obj-y += core_parking.o
+obj-$(HAS_CORE_PARKING) += core_parking.o
 obj-y += cpu.o
 obj-y += cpupool.o
 obj-$(HAS_DEVICE_TREE) += device_tree.o