kernel: lantiq: vrx518_tc: add patch fix compilation warning for ptm_tc

kernel: lantiq: vrx518_tc: add patch fix compilation warning for ptm_tc

Alloc MIB struct dynamically instead to fix compilation warning for
stack limit.
Fix compilation warning:
/__w/openwrt/openwrt/openwrt/build_dir/target-arm-openwrt-linux-muslgnueabi_musl/linux-ipq40xx_chromium/vrx518_tc_drv-ugw_8.5.2.10/dcdp/ptm_tc.c: In function 'ptm_tc_get_stats':
/__w/openwrt/openwrt/openwrt/build_dir/target-arm-openwrt-linux-muslgnueabi_musl/linux-ipq40xx_chromium/vrx518_tc_drv-ugw_8.5.2.10/dcdp/ptm_tc.c:463:1: error: the frame size of 1032 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
  463 | }
      | ^
cc1: all warnings being treated as errors

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>