lwip: struct netif->hostname can be a const pointer
lwip: struct netif->hostname can be a const pointer

Upstream commit: 91b6d4517898db874d34b04a78a5946e993caea5

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