microblaze: Add .gitignore entries for auto-generated files

Add .gitignore entries for files which are generated during the build process.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
diff --git a/arch/microblaze/boot/.gitignore b/arch/microblaze/boot/.gitignore
new file mode 100644
index 0000000..bf04591
--- /dev/null
+++ b/arch/microblaze/boot/.gitignore
@@ -0,0 +1,3 @@
+*.dtb
+linux.bin*
+simpleImage.*