xen/arm/arm64: merge xen/mm32.c into xen/mm.c

Merge xen/mm32.c into xen/mm.c.
As a consequence the code gets compiled on arm64 too.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm/xen/Makefile b/arch/arm/xen/Makefile
index 1f85bfe..1296952 100644
--- a/arch/arm/xen/Makefile
+++ b/arch/arm/xen/Makefile
@@ -1 +1 @@
-obj-y		:= enlighten.o hypercall.o grant-table.o p2m.o mm.o mm32.o
+obj-y		:= enlighten.o hypercall.o grant-table.o p2m.o mm.o