tools: Add entry for generated tools/bin2header to tools/.gitignore

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>

tools/.gitignore

@@ -1,4 +1,5 @@
 /atmel_pmecc_params
+/bin2header
 /bmp_logo
 /envcrc
 /fdtgrep