efidebug: avoid 'dfu_alt_info not defined' message

If variable dfu_alt_info is not defined duplicate messages are displayed.

    => efidebug boot dump
    Scanning disk mmc2.blk...
    Scanning disk mmc1.blk...
    Scanning disk mmc0.blk...
    Found 3 disks
    No EFI system partition
    "dfu_alt_info" env variable not defined!
    Probably dfu_alt_info not defined
    "dfu_alt_info" env variable not defined!
    Probably dfu_alt_info not defined

Remove the 'Probably dfu_alt_info not defined' message.
Instead write a warning if the variable contains no entities.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/efi_firmware.c b/lib/efi_loader/efi_firmware.c
index a1b88db..519a472 100644
--- a/lib/efi_loader/efi_firmware.c
+++ b/lib/efi_loader/efi_firmware.c
@@ -128,8 +128,11 @@
 	size_t names_len, total_size;
 	int dfu_num, i;
 	u16 *name, *next;
+	int ret;
 
-	dfu_init_env_entities(NULL, NULL);
+	ret = dfu_init_env_entities(NULL, NULL);
+	if (ret)
+		return EFI_SUCCESS;
 
 	names_len = 0;
 	dfu_num = 0;
@@ -138,7 +141,7 @@
 		dfu_num++;
 	}
 	if (!dfu_num) {
-		log_warning("Probably dfu_alt_info not defined\n");
+		log_warning("No entities in dfu_alt_info\n");
 		*image_info_size = 0;
 		dfu_free_entities();