net_lwip_webserver example fix and improvement #512

Job	Run time
set-matrix	3s
build (esp-idf) / family (-b espressif_p4_function_ev)	8m 40s
build (esp-idf) / family (-b espressif_p4_function_ev -f1 CFG_TUD_DWC2_DMA_ENABLE -f1 CFG_TUH_DWC2_DMA_ENABLE)	8m 32s
build (esp-idf) / family (-b espressif_s3_devkitm)	8m 7s
build (esp-idf) / family (-b espressif_s3_devkitm -f1 CFG_TUD_DWC2_DMA_ENABLE)	8m 15s
build (arm-gcc) / family (-b feather_nrf52840_express)	1m 1s
build (arm-gcc) / family (-b max32666fthr)	1m 16s
build (arm-gcc) / family (-b metro_m4_express)	59s
build (arm-gcc) / family (-b lpcxpresso11u37)	30s
build (arm-gcc) / family (-b ra4m1_ek)	37s
build (arm-gcc) / family (-b raspberry_pi_pico)	2m 5s
build (arm-gcc) / family (-b raspberry_pi_pico2)	2m 24s
build (arm-gcc) / family (-b stm32f072disco)	34s
build (arm-gcc) / family (-b stm32f723disco)	49s
build (arm-gcc) / family (-b stm32f723disco -f1 CFG_TUH_DWC2_DMA_ENABLE)	49s
build (arm-gcc) / family (-b stm32h743nucleo)	50s
build (arm-gcc) / family (-b stm32h743nucleo -f1 CFG_TUD_DWC2_DMA_ENABLE)	47s
build (arm-gcc) / family (-b stm32g0b1nucleo)	45s
hil-tinyusb	2m 10s
	49m 13s

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