ltq-ptm: vdsl: fix 6.12 kernel build errors on lantiq/xrx200

Add missing header to fix the build errors on 6.12 kernel.

Signed-off-by: Shiji Yang <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/18744
Signed-off-by: Robert Marko <[email protected]>
(cherry picked from commit b48ed6d19c3a72b203faf3b62432026f2ce48d0a)
Signed-off-by: Nora Matthias Schiffer <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20440
Signed-off-by: Hauke Mehrtens <[email protected]>

package/kernel/lantiq/ltq-ptm/patches/103-add-missing-header-mod_devicetable.h.patch

@@ -0,0 +1,26 @@
+From: Shiji Yang <[email protected]>
+Date: Fri, 9 May 2025 02:36:31 +0800
+Subject: [PATCH] add missing header mod_devicetable.h
+
+Fix compilation error:
+
+/home/db/owrt/build_dir/target-mips_24kc_musl/linux-lantiq_xrx200/ltq-ptm-vr9/ltq-ptm/ifxmips_ptm_vdsl.c:969:34: error: array type has incomplete element type 'struct of_device_id'
+  969 | static const struct of_device_id ltq_ptm_match[] = {
+      |                                  ^~~~~~~~~~~~~
+/home/db/owrt/build_dir/target-mips_24kc_musl/linux-lantiq_xrx200/ltq-ptm-vr9/ltq-ptm/ifxmips_ptm_vdsl.c:969:34: error: 'ltq_ptm_match' defined but not used [-Werror=unused-variable]
+
+Signed-off-by: Shiji Yang <[email protected]>
+---
+ ifxmips_ptm_vdsl.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+--- a/ifxmips_ptm_vdsl.c
++++ b/ifxmips_ptm_vdsl.c
+@@ -34,6 +34,7 @@
+ #include <linux/interrupt.h>
+ #include <linux/netdevice.h>
+ #include <linux/platform_device.h>
++#include <linux/mod_devicetable.h>
+ #include <linux/of_device.h>
+ 
+ #include "ifxmips_ptm_vdsl.h"