tools: add ncb to gitignore

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

tools/.gitignore

@@ -4,6 +4,7 @@
 /img2srec
 /mkimage
 /mpc86x_clk
+/ncb
 /ncp
 /ubsha1
 /inca-swap-bytes