remove duplicates of new generic bits/sem.h

some of these were not exact duplicates, but had gratuitously
different naming for padding, or omitted the endian checks because the
arch is fixed-endian.

arch/aarch64/bits/sem.h

-struct semid_ds {
-	struct ipc_perm sem_perm;
-	time_t sem_otime;
-	time_t sem_ctime;
-#if __BYTE_ORDER == __LITTLE_ENDIAN
-	unsigned short sem_nsems;
-	char __sem_nsems_pad[sizeof(long)-sizeof(short)];
-#else
-	char __sem_nsems_pad[sizeof(long)-sizeof(short)];
-	unsigned short sem_nsems;
-#endif
-	long __unused3;
-	long __unused4;
-};

arch/mips64/bits/sem.h

-struct semid_ds {
-	struct ipc_perm sem_perm;
-	time_t sem_otime;
-	time_t sem_ctime;
-#if __BYTE_ORDER == __LITTLE_ENDIAN
-	unsigned short sem_nsems;
-	char __sem_nsems_pad[sizeof(long)-sizeof(short)];
-#else
-	char __sem_nsems_pad[sizeof(long)-sizeof(short)];
-	unsigned short sem_nsems;
-#endif
-	long __unused3;
-	long __unused4;
-};

arch/powerpc64/bits/sem.h

-#include <endian.h>
-
-struct semid_ds {
-	struct ipc_perm sem_perm;
-	time_t sem_otime;
-	time_t sem_ctime;
-#if __BYTE_ORDER == __BIG_ENDIAN
-	unsigned short __pad[3], sem_nsems;
-#else
-	unsigned short sem_nsems, __pad[3];
-#endif
-	unsigned long __unused[2];
-};

arch/riscv64/bits/sem.h

-struct semid_ds {
-	struct ipc_perm sem_perm;
-	time_t sem_otime;
-	time_t sem_ctime;
-	unsigned short sem_nsems;
-	char __sem_nsems_pad[sizeof(long)-sizeof(short)];
-	long __unused3;
-	long __unused4;
-};

arch/s390x/bits/sem.h

-struct semid_ds {
-	struct ipc_perm sem_perm;
-	time_t sem_otime;
-	time_t sem_ctime;
-	unsigned short __pad[3], sem_nsems;
-	unsigned long __unused[2];
-};