powerpc: Use vsprintf extention %pf with builtin_return_address

Emit the function name not the address when possible.

builtin_return_address() gives an address.  When building
a kernel with CONFIG_KALLSYMS, emit the actual function
name not the address.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/pgtable_32.c

@@ -207,7 +207,7 @@ __ioremap_caller(phys_addr_t addr, unsigned long size, unsigned long flags,
 	 */
 	if (mem_init_done && (p < virt_to_phys(high_memory)) &&
 	    !(__allow_ioremap_reserved && memblock_is_region_reserved(p, size))) {
-		printk("__ioremap(): phys addr 0x%llx is RAM lr %p\n",
+		printk("__ioremap(): phys addr 0x%llx is RAM lr %pf\n",
 		       (unsigned long long)p, __builtin_return_address(0));
 		return NULL;
 	}