Ignore lo.png output from make dump-deps-png

Change-Id: I9d968a14db440a54e3accefb12e2d0a5685d0b37
diff --git a/.gitignore b/.gitignore
index 2370081..01e57e1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -140,6 +140,9 @@ DerivedData
# doxygen output
/docs

# make dump-deps output
/lo.png

# gdb config
/.gdbinit
/.gdb_history