[POWERPC] Add treeImage to .gitignore

Tell git to ignore the generated treeImage.* files in arch/powerpc/boot

Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
diff --git a/arch/powerpc/boot/.gitignore b/arch/powerpc/boot/.gitignore
index 2c187ca..65f4118 100644
--- a/arch/powerpc/boot/.gitignore
+++ b/arch/powerpc/boot/.gitignore
@@ -19,6 +19,7 @@
 mktree
 uImage
 cuImage.*
+treeImage.*
 zImage
 zImage.bin.*
 zImage.chrp