net: lwip: fix get_udev_ipv4_info()

net: lwip: fix get_udev_ipv4_info()

The local variables ipstr, maskstr and gwstr in static function
get_udev_ipv4_info() cannot be pointers to read-only data, since
they may be written to in case the device index is > 0. Therefore
make them char arrays allocated on the stack.

Reported-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reported-by: Adriano Cordova <adrianox@gmail.com>
Link: https://lists.denx.de/pipermail/u-boot/2024-November/572066.html
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>