powerpc: Fix unused function warning 'lmb_to_memblock'

This patch fixes the following warning:
arch/powerpc/platforms/pseries/hotplug-memory.c:323:29: error: 'lmb_to_memblock' defined but not used [-Werror=unused-function]
static struct memory_block *lmb_to_memblock(struct of_drconf_cell *lmb)
                           ^~~~~~~~~~~~~~~

The only consumer of this function is 'dlpar_remove_lmb', which is
enabled with CONFIG_MEMORY_HOTREMOVE, so move it into the same
ifdef block.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/pseries/hotplug-memory.c

@@ -320,19 +320,6 @@ static int dlpar_remove_device_tree_lmb(struct of_drconf_cell *lmb)
 	return dlpar_update_device_tree_lmb(lmb);
 }
 
-static struct memory_block *lmb_to_memblock(struct of_drconf_cell *lmb)
-{
-	unsigned long section_nr;
-	struct mem_section *mem_sect;
-	struct memory_block *mem_block;
-
-	section_nr = pfn_to_section_nr(PFN_DOWN(lmb->base_addr));
-	mem_sect = __nr_to_section(section_nr);
-
-	mem_block = find_memory_block(mem_sect);
-	return mem_block;
-}
-
 #ifdef CONFIG_MEMORY_HOTREMOVE
 static int pseries_remove_memblock(unsigned long base, unsigned int memblock_size)
 {
@@ -420,6 +407,19 @@ static bool lmb_is_removable(struct of_drconf_cell *lmb)
 
 static int dlpar_add_lmb(struct of_drconf_cell *);
 
+static struct memory_block *lmb_to_memblock(struct of_drconf_cell *lmb)
+{
+	unsigned long section_nr;
+	struct mem_section *mem_sect;
+	struct memory_block *mem_block;
+
+	section_nr = pfn_to_section_nr(PFN_DOWN(lmb->base_addr));
+	mem_sect = __nr_to_section(section_nr);
+
+	mem_block = find_memory_block(mem_sect);
+	return mem_block;
+}
+
 static int dlpar_remove_lmb(struct of_drconf_cell *lmb)
 {
 	struct memory_block *mem_block;