build: remove ac_cv_header_netinet_sctp_h=no from pre-cached variables

We have <netinet/sctp.h> header in lksctp-tools package,
but having this var set to 'no' prevents package's configure
to detect it.

Signed-off-by: Aleksey Vasilenko <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/16441
Signed-off-by: Hauke Mehrtens <[email protected]>

include/site/linux

@@ -53,7 +53,6 @@ ac_cv_have_control_in_msghdr=yes
 ac_cv_have_decl_sys_siglist=no
 ac_cv_have_openpty_ctty_bug=yes
 ac_cv_have_space_d_name_in_struct_dirent=yes
-ac_cv_header_netinet_sctp_h=no
 ac_cv_header_netinet_sctp_uio_h=no
 ac_cv_int64_t=yes
 ac_cv_lbl_unaligned_fail=no