core: fdtaddr: use map_sysmem() as cast for the return (part 2)

For the devfdt_get_addr_size_index_ptr() function use
map_sysmem() function as cast for the return for use in
sandbox.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
diff --git a/drivers/core/fdtaddr.c b/drivers/core/fdtaddr.c
index 3b59b70..546db67 100644
--- a/drivers/core/fdtaddr.c
+++ b/drivers/core/fdtaddr.c
@@ -131,7 +131,10 @@
 {
 	fdt_addr_t addr = devfdt_get_addr_size_index(dev, index, size);
 
-	return (addr == FDT_ADDR_T_NONE) ? NULL : (void *)(uintptr_t)addr;
+	if (addr == FDT_ADDR_T_NONE)
+		return NULL;
+
+	return map_sysmem(addr, 0);
 }
 
 fdt_addr_t devfdt_get_addr_name(const struct udevice *dev, const char *name)