extmod/modlwip: Remove unused include and functions.

The lwIP includes are now port-specific.

The `sys_arch_{,un}protect` functions are not used according to line 34
of `extmod/lwip-include/lwipopts_common.h`.

Neither have been touched in nearly a decade.

Signed-off-by: Thomas Watson <twatson52@icloud.com>

Author: tpwrules

extmod/lwip-include/arch/cc.h

@@ -1724,18 +1724,6 @@ static MP_DEFINE_CONST_OBJ_TYPE(
     locals_dict, &lwip_socket_locals_dict
     );
 
-/******************************************************************************/
-// Support functions for memory protection. lwIP has its own memory management
-// routines for its internal structures, and since they might be called in
-// interrupt handlers, they need some protection.
-sys_prot_t sys_arch_protect() {
-    return (sys_prot_t)MICROPY_BEGIN_ATOMIC_SECTION();
-}
-
-void sys_arch_unprotect(sys_prot_t state) {
-    MICROPY_END_ATOMIC_SECTION((mp_uint_t)state);
-}
-
 /******************************************************************************/
 // Polling callbacks for the interfaces connected to lwIP. Right now it calls
 // itself a "list" but isn't; we only support a single interface.