configs: Enable progress meter for TFTP

This enables Petitboot after v1.4.0 to do fancy UI things with Busybox
utilities.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
diff --git a/openpower/configs/busybox.fragment b/openpower/configs/busybox.fragment
new file mode 100644
index 0000000..1b13459
--- /dev/null
+++ b/openpower/configs/busybox.fragment
@@ -0,0 +1 @@
+CONFIG_FEATURE_TFTP_PROGRESS_BAR=y