xen/balloon: Fix declared-but-not-defined warning

Fix a declared-but-not-defined warning when building with
XEN_BALLOON_MEMORY_HOTPLUG=n. This fixes a regression introduced by
commit dfd74a1e ("xen/balloon: Fix crash when ballooning on x86 32
bit PAE").
Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Acked-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

drivers/xen/balloon.c

@@ -151,8 +151,6 @@ static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
 static void balloon_process(struct work_struct *work);
 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
 
-static void release_memory_resource(struct resource *resource);
-
 /* When ballooning out (allocating memory to return to Xen) we don't really
    want the kernel to try too hard since that can trigger the oom killer. */
 #define GFP_BALLOON \
@@ -248,6 +246,19 @@ static enum bp_state update_schedule(enum bp_state state)
 }
 
 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
+static void release_memory_resource(struct resource *resource)
+{
+	if (!resource)
+		return;
+
+	/*
+	 * No need to reset region to identity mapped since we now
+	 * know that no I/O can be in this region
+	 */
+	release_resource(resource);
+	kfree(resource);
+}
+
 static struct resource *additional_memory_resource(phys_addr_t size)
 {
 	struct resource *res;
@@ -286,19 +297,6 @@ static struct resource *additional_memory_resource(phys_addr_t size)
 	return res;
 }
 
-static void release_memory_resource(struct resource *resource)
-{
-	if (!resource)
-		return;
-
-	/*
-	 * No need to reset region to identity mapped since we now
-	 * know that no I/O can be in this region
-	 */
-	release_resource(resource);
-	kfree(resource);
-}
-
 static enum bp_state reserve_additional_memory(void)
 {
 	long credit;