vbe: Avoid accessing TEXT_BASE if undefined

Use a condition to ensure this symbol is not accessed in the EFI app.

Signed-off-by: Simon Glass <sjg@chromium.org>

boot/vbe_common.c

@@ -174,7 +174,7 @@ int vbe_read_fit(struct udevice *blk, ulong area_offset, ulong area_size,
 	 * external data, so this is quite small, perhaps a few KB.
 	 */
 	if (IS_ENABLED(CONFIG_SANDBOX)) {
-		addr = CONFIG_VAL(TEXT_BASE);
+		addr = IF_ENABLED_INT(CONFIG_SANDBOX, CONFIG_VAL(TEXT_BASE));
 		buf = map_sysmem(addr, size);
 	} else {
 		buf = malloc(aligned_size);