efi_loader: efi_disk_register() should not fail

Our algorithm for creating USB device paths may lead to duplicate device
paths which result in efi_disk_register() failing. Instead we should just
skip devices that cannot be registered as EFI block devices.

Fix a memory leak in efi_disk_add_dev() caused by the duplicate device
path.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c
index ef8b5c8..45127d1 100644
--- a/lib/efi_loader/efi_disk.c
+++ b/lib/efi_loader/efi_disk.c
@@ -424,7 +424,7 @@
 			&efi_block_io_guid, &diskobj->ops,
 			guid, NULL, NULL));
 	if (ret != EFI_SUCCESS)
-		return ret;
+		goto error;
 
 	/*
 	 * On partitions or whole disks without partitions install the
@@ -573,7 +573,7 @@
 		if (ret) {
 			log_err("ERROR: failure to add disk device %s, r = %lu\n",
 				dev->name, ret & ~EFI_ERROR_MASK);
-			return ret;
+			continue;
 		}
 		disks++;