dt-bindings: Fix .gitignore

The tracked files should not be ignored.

Fixes: 44ec8b20 ("dt-bindings: Add running yamllint to dt_binding_check")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230127150225.18148-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Rob Herring <robh@kernel.org>