ipq806x: tr4400v2: fix dtc warnings by deleting stock partitions

ipq806x: tr4400v2: fix dtc warnings by deleting stock partitions

The original set of stock partitions was kept in the TR4400 v2 port,
with the same partition numbers but their names prefixed with 'stock_'.
This allowed scripts (installation, back to stock, etc) to run on both
stock and OpenWrt firmware. But this triggers warnings in the device
tree compiler, as partitions of the old and new schemes overlap.

This commit fixes the dtc warnings by deleting the stock partitions,
also renumbering some of the remaining MTD partitions in the process.
Additionally, the 'fw_env' partition is set to read-only.

These changes can break existing scripts as well as user configurations
that utilize the 'extra' partition. Users wanting to run old scripts can
do so by reverting to the 23.05 series releases.

Signed-off-by: Rodrigo Balerdi <lanchon@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/16958
Signed-off-by: Robert Marko <robimarko@gmail.com>