.gitignore: ignore generated u-boot.imx

Signed-off-by: Stefano Babic <sbabic@denx.de>
diff --git a/.gitignore b/.gitignore
index e71f6ac..8ec3d06 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,6 +21,7 @@
 /System.map
 /u-boot
 /u-boot.hex
+/u-boot.imx
 /u-boot.map
 /u-boot.bin
 /u-boot.srec