efi: sandbox: Enable selftest command

Enable this for sandbox since it almost passes now.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index ca12118..0b20968 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -23,6 +23,7 @@
 CONFIG_CMD_CPU=y
 CONFIG_CMD_LICENSE=y
 CONFIG_CMD_BOOTZ=y
+CONFIG_CMD_BOOTEFI_SELFTEST=y
 # CONFIG_CMD_ELF is not set
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_GREPENV=y