lwip: tcp: fixed TCPH_UNSET_FLAG macro
lwip: tcp: fixed TCPH_UNSET_FLAG macro

Upstream commit: 733758a9094920e5f8fbd7241613fbfc2a3ef8d8

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