drivers/i2c: Include SPDX-license-identifier

including the SPDX license identifier header makes it easy for developers and machines to know the lecense that is governing the file

---
 drivers/i2c/i2c-core-slave.c | 1 +
 1 file changed, 1 insertion(+)

index 4a78c65..883ca836 100644
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Linux I2C core slave support code
  *

2.7.4

If you do changes like this, you should also remove the actual license text (it follows later in the comment in this case). And more importantly, you should make *sure* that you use the correct SPDX tag, which you don't in this case.

So, you need to fix those issues.

Cheers,
Peter