lwip: tcp_alloc(): remove explicit =0 already done by memset(0)
lwip: tcp_alloc(): remove explicit =0 already done by memset(0)

Upstream commit: 5794ac2340f26e14dc78882aceffcc75db153d6e

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