[fusl] Remove socketcall abstraction

fusl/src/network/accept4.c

 #define _GNU_SOURCE
 #include <sys/socket.h>
 #include <errno.h>
 #include <fcntl.h>
 #include "syscall.h"
 #include "libc.h"
 
 int accept4(int fd,
             struct sockaddr* restrict addr,
             socklen_t* restrict len,
             int flg) {
   if (!flg)
     return accept(fd, addr, len);
-  int ret = socketcall_cp(accept4, fd, addr, len, flg, 0, 0);
+  int ret = syscall_cp(SYS_accept4, fd, addr, len, flg, 0, 0);
   if (ret >= 0 || (errno != ENOSYS && errno != EINVAL))
     return ret;
   ret = accept(fd, addr, len);
   if (ret < 0)
     return ret;
   if (flg & SOCK_CLOEXEC)
     __syscall(SYS_fcntl, ret, F_SETFD, FD_CLOEXEC);
   if (flg & SOCK_NONBLOCK)
     __syscall(SYS_fcntl, ret, F_SETFL, O_NONBLOCK);
   return ret;
 }