.gitignore: Ignore .img files

The generated idbloader.img file that rockchip uses should
be not included in git status report

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
diff --git a/.gitignore b/.gitignore
index d8b7b77..f980ae6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,6 +17,7 @@
 *.gcda
 *.gcno
 *.i
+*.img
 *.lex.c
 *.lst
 *.mod.c