gitignore: Add defconfig and fdtgrep

Ignore defconfig and tools/fdtgrep.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/.gitignore b/tools/.gitignore
index eb1a27e..ff07680 100644
--- a/tools/.gitignore
+++ b/tools/.gitignore
@@ -1,6 +1,7 @@
 /atmel_pmecc_params
 /bmp_logo
 /envcrc
+/fdtgrep
 /fit_check_sign
 /fit_info
 /gen_eth_addr