CLEANUP: conn_stream: apply cs_endp_flags.cocci tree-wide

CLEANUP: conn_stream: apply cs_endp_flags.cocci tree-wide

This changes all main uses of cs->endp->flags to the sc_ep_*() equivalent
by applying coccinelle script cs_endp_flags.cocci.

Note: 143 locations were touched, manually reviewed and found to be OK,
except a single one that was adjusted in cs_reset_endp() where the flags
are read and filtered to be used as-is and not as a boolean, hence was
replaced with sc_ep_get() & $FLAGS.

The script was applied with all includes:

  spatch --in-place --recursive-includes -I include --sp-file $script $files