.gitignore: add SPDX License Identifier

Add SPDX License Identifier to all .gitignore files.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/crypto/vmx/.gitignore b/drivers/crypto/vmx/.gitignore
index af4a7ce..7aa71d8 100644
--- a/drivers/crypto/vmx/.gitignore
+++ b/drivers/crypto/vmx/.gitignore
@@ -1,2 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
 aesp8-ppc.S
 ghashp8-ppc.S