kernel: bump 6.12 to 6.12.29

kernel: bump 6.12 to 6.12.29

Changelog: https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.12.29

Removed upstreamed:
        generic/pending-6.12/730-net-ethernet-mtk_eth_soc-reset-all-TX-queues-on-DMA-.patch[1]

Added settings:
        x86: CONFIG_MITIGATION_ITS=y[2]

1. https://web.git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-6.12.y&id=aac9d5fa537b0c19f6d3af3c8a124028510bb647
2. https://web.git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-6.12.y&id=68d59e9ba38424389168eddf8791265818f67292

All other patches automatically rebased.

Build system: x86/64
Build-tested: x86/64
Run-tested: x86/64

Signed-off-by: Mieczyslaw Nalewaj <namiltd@yahoo.com>
Link: https://github.com/openwrt/openwrt/pull/18837
Signed-off-by: Robert Marko <robimarko@gmail.com>