Rename --use_hex to --hex

This is much more common on unix systems, and I end up typing it by
accident most of the time.  And it is shorter too.

Change-Id: I8e4bbc186a8a82c7546d74e161c145825f0c4c0f
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/aos/aos_cli_utils.h b/aos/aos_cli_utils.h
index 9082188..35fb61f 100644
--- a/aos/aos_cli_utils.h
+++ b/aos/aos_cli_utils.h
@@ -23,7 +23,7 @@
   // Print the distributed clock.
   bool distributed_clock;
   // Print numbers out in hex.
-  bool use_hex;
+  bool hex;
 };
 
 // Print the flatbuffer out to stdout, both to remove the unnecessary cruft from