tools: Add ifwitool to .gitignore

Follow up fix to the commit

56bf4f863075 ("x86: Add ifwitool for Intel Integrated Firmware Image")

in order to ignore created binary.

Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/tools/.gitignore b/tools/.gitignore
index 767b056..bd03d32 100644
--- a/tools/.gitignore
+++ b/tools/.gitignore
@@ -14,6 +14,7 @@
 /gen_eth_addr
 /gen_ethaddr_crc
 /ifdtool
+/ifwitool
 /img2srec
 /kwboot
 /lib/