.gitignore: prefix local generated files with a slash

The pattern prefixed with '/' matches files in the same directory,
but not ones in sub-directories.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Andra Paraschiv <andraprs@amazon.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Gabriel Krisman Bertazi <krisman@collabora.com>
diff --git a/kernel/.gitignore b/kernel/.gitignore
index dafdce3..c6b299a 100644
--- a/kernel/.gitignore
+++ b/kernel/.gitignore
@@ -1,3 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 /config_data
-kheaders.md5
+/kheaders.md5