xen: make direct versions of irq_enable/disable/save/restore to common code

Now that x86-64 has directly accessible percpu variables, it can also
implement the direct versions of these operations, which operate on a
vcpu_info structure directly embedded in the percpu area.

In fact, the 64-bit versions are more or less identical, and so can be
shared.  The only two differences are:
 1. xen_restore_fl_direct takes its argument in eax on 32-bit, and rdi on 64-bit.
    Unfortunately it isn't possible to directly refer to the 2nd lsb of rdi directly
    (as you can with %ah), so the code isn't quite as dense.
 2. check_events needs to variants to save different registers.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index 6dcefba..3b767d0 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -6,7 +6,8 @@
 endif
 
 obj-y		:= enlighten.o setup.o multicalls.o mmu.o irq.o \
-			time.o xen-asm_$(BITS).o grant-table.o suspend.o
+			time.o xen-asm.o xen-asm_$(BITS).o \
+			grant-table.o suspend.o
 
 obj-$(CONFIG_SMP)		+= smp.o spinlock.o
 obj-$(CONFIG_XEN_DEBUG_FS)	+= debugfs.o
\ No newline at end of file