lwip: dns: Use LWIP_ARRAYSIZE instead of open coded
lwip: dns: Use LWIP_ARRAYSIZE instead of open coded

Upstream commit: 8c0f620d83f13078e087351351ca9f9890d521af

ambrop72/aprinter,ambrop72/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,ambrop72/aprinter,johnkingsley/aprinter,ambrop72/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,ambrop72/aprinter,johnkingsley/aprinter,ambrop72/aprinter,ambrop72/aprinter