[SPARC64]: Allow CONFIG_MEMORY_HOTPLUG to build.

online_page() is straightforward, and then add a dummy
remove_memory() that returns -EINVAL just like i386.

There is no point in implementing remove_memory() since
__remove_pages() has no implementation either.
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc64/mm/init.c

@@ -1805,3 +1805,21 @@ void __flush_tlb_all(void)
 	__asm__ __volatile__("wrpr	%0, 0, %%pstate"
 			     : : "r" (pstate));
 }
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+
+void online_page(struct page *page)
+{
+	ClearPageReserved(page);
+	set_page_count(page, 0);
+	free_cold_page(page);
+	totalram_pages++;
+	num_physpages++;
+}
+
+int remove_memory(u64 start, u64 size)
+{
+	return -EINVAL;
+}
+
+#endif /* CONFIG_MEMORY_HOTPLUG */