Revert "Switch to toybox ls."

This reverts commit 9c94aa9982c562585c08c5f95569695ccc64f846.

Change-Id: Ie2479ee4a0614e285ce8d57c727200a0381904e2
diff --git a/toolbox/Android.mk b/toolbox/Android.mk
index 5a58d19..ad99a39 100644
--- a/toolbox/Android.mk
+++ b/toolbox/Android.mk
@@ -45,6 +45,7 @@
     ioctl \
     ionice \
     log \
+    ls \
     lsof \
     mount \
     nandread \