[fusl] Remove code for unsupported architectures

fusl/arch/powerpc/bits/socket.h

-struct msghdr {
-  void* msg_name;
-  socklen_t msg_namelen;
-  struct iovec* msg_iov;
-  int msg_iovlen;
-  void* msg_control;
-  socklen_t msg_controllen;
-  int msg_flags;
-};
-
-struct cmsghdr {
-  socklen_t cmsg_len;
-  int cmsg_level;
-  int cmsg_type;
-};
-
-#define SO_DEBUG 1
-#define SO_REUSEADDR 2
-#define SO_TYPE 3
-#define SO_ERROR 4
-#define SO_DONTROUTE 5
-#define SO_BROADCAST 6
-#define SO_SNDBUF 7
-#define SO_RCVBUF 8
-#define SO_KEEPALIVE 9
-#define SO_OOBINLINE 10
-#define SO_NO_CHECK 11
-#define SO_PRIORITY 12
-#define SO_LINGER 13
-#define SO_BSDCOMPAT 14
-#define SO_REUSEPORT 15
-#define SO_RCVLOWAT 16
-#define SO_SNDLOWAT 17
-#define SO_RCVTIMEO 18
-#define SO_SNDTIMEO 19
-#define SO_PASSCRED 20
-#define SO_PEERCRED 21
-#define SO_ACCEPTCONN 30
-#define SO_SNDBUFFORCE 32
-#define SO_RCVBUFFORCE 33
-#define SO_PROTOCOL 38
-#define SO_DOMAIN 39