image: Rename load_addr, save_addr, save_size

These global variables are quite short and generic. In fact the same name
is more often used locally for struct members and function arguments.

Add a image_ prefix to make them easier to distinguish.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/pxe_utils.c b/cmd/pxe_utils.c
index a636346..ff8b0dc 100644
--- a/cmd/pxe_utils.c
+++ b/cmd/pxe_utils.c
@@ -1310,9 +1310,9 @@
 #ifdef CONFIG_CMD_BMP
 	/* display BMP if available */
 	if (cfg->bmp) {
-		if (get_relfile(cmdtp, cfg->bmp, load_addr)) {
+		if (get_relfile(cmdtp, cfg->bmp, image_load_addr)) {
 			run_command("cls", 0);
-			bmp_display(load_addr,
+			bmp_display(image_load_addr,
 				    BMP_ALIGN_CENTER, BMP_ALIGN_CENTER);
 		} else {
 			printf("Skipping background bmp %s for failure\n",