lwip/wifi: Fix crashes during reinitialisation of wi-fi #217

Job	Run time
call-ci / build (armv7a7-imx6ull-evk)	1m 23s
call-ci / build (armv7a9-zynq7000-qemu)	1m 52s
call-ci / build (armv7a9-zynq7000-zedboard)	2m 49s
call-ci / build (armv7a9-zynq7000-zturn)	1m 17s
call-ci / build (armv7m4-stm32l4x6-nucleo)	1m 5s
call-ci / build (armv7m7-imxrt105x-evk)	1m 25s
call-ci / build (armv7m7-imxrt106x-evk)	1m 13s
call-ci / build (armv7m7-imxrt117x-evk)	1m 18s
call-ci / build (host-generic-pc)	54s
call-ci / build (ia32-generic-pc)	1m 15s
call-ci / build (ia32-generic-qemu)	1m 19s
call-ci / build (riscv64-generic-qemu)	1m 7s
call-ci / build (riscv64-generic-spike)	1m 4s
call-ci / build (sparcv8leon3-gr716-mini)	1m 10s
call-ci / test HW (armv7a7-imx6ull-evk)	5m 35s
call-ci / test EMU (armv7a9-zynq7000-qemu)	9m 1s
call-ci / test HW (armv7m7-imxrt106x-evk)	2m 54s
call-ci / test EMU (host-generic-pc)	57s
call-ci / test HW (armv7m7-imxrt117x-evk)	2m 55s
call-ci / test EMU (ia32-generic-qemu)	5m 43s
call-ci / test HW (armv7a9-zynq7000-zedboard)	5m 58s
call-ci / test EMU (riscv64-generic-qemu)	2m 43s
call-ci / test HW (armv7m4-stm32l4x6-nucleo)	10m 12s
call-ci / tests-summary	28s
call-ci / send-notification	0s
	1h 5m 37s

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