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/load.c b/cmd/load.c
index 68ff301..bed973e 100644
--- a/cmd/load.c
+++ b/cmd/load.c
@@ -109,7 +109,7 @@
 		rcode = 1;
 	} else {
 		printf("## Start Addr      = 0x%08lX\n", addr);
-		load_addr = addr;
+		image_load_addr = addr;
 	}
 
 #ifdef	CONFIG_SYS_LOADS_BAUD_CHANGE
@@ -485,12 +485,12 @@
 		addr = load_serial_bin(offset);
 
 		if (addr == ~0) {
-			load_addr = 0;
+			image_load_addr = 0;
 			printf("## Binary (kermit) download aborted\n");
 			rcode = 1;
 		} else {
 			printf("## Start Addr      = 0x%08lX\n", addr);
-			load_addr = addr;
+			image_load_addr = addr;
 		}
 	}
 	if (load_baudrate != current_baudrate) {