[PATCH v3] .gitattributes: use 'dts' diff driver for *.dtso files

[Masahiro Yamada]

Now we have the third extension for DT source files (overlay).
Give the diff=dts attribute to *.dtso as well.

While I was here, I merged *.c and *.o into *.[ch] and added the
SPDX-License-Identifier.

Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---

Changes in v3:
  - Add SPDX-License-Identifier

Changes in v2:
  - Slightly shorten the code

 .gitattributes | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/.gitattributes b/.gitattributes
index 4b32eaa9571e..c9ba5bfc4036 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1,4 +1,4 @@
-*.c   diff=cpp
-*.h   diff=cpp
-*.dtsi diff=dts
-*.dts  diff=dts
+# SPDX-License-Identifier: GPL-2.0-only
+*.[ch] diff=cpp
+*.dts diff=dts
+*.dts[io] diff=dts
-- 
2.34.1