efi: sandbox: Enable selftest command

Enable this for sandbox since it almost passes now.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Signed-off-by: NAlexander Graf <agraf@suse.de>

configs/sandbox_defconfig

@@ -23,6 +23,7 @@ CONFIG_DISPLAY_BOARDINFO_LATE=y
 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