.gitignore: move *.dtb and *.dtb.S patterns to the top-level .gitignore

Follow Linux commit 10b62a2f785a (".gitignore: move *.dtb and *.dtb.S
patterns to the top-level .gitignore").

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
9 files changed