kernel: add missing patch header

Make sure all patches can again be applied using 'git am' on the
corresponding linux-stable git tree.

Fixes: a7ae4ed0a3 ("kernel: fix tools build breakage on macos with x86")
Signed-off-by: Daniel Golle <[email protected]>

target/linux/generic/hack-6.6/200-tools_portability.patch

@@ -1,3 +1,10 @@
+From a7ae4ed0a3951c45d4a59ee575951b64ae4a23fb Mon Sep 17 00:00:00 2001
+From: Felix Fietkau <[email protected]>
+Date: Tue, 7 May 2024 12:22:15 +0200
+Subject: [PATCH] kernel: fix tools build breakage on macos with x86
+
+Signed-off-by: Felix Fietkau <[email protected]>
+---
 --- a/tools/scripts/Makefile.include
 +++ b/tools/scripts/Makefile.include
 @@ -72,8 +72,6 @@ $(call allow-override,CXX,$(CROSS_COMPIL