Partial revert of "powerpc: Individual System V IPC system calls"

This partially reverts commit a3423615

.

While reviewing the glibc patch to exploit the individual IPC calls,
Arnd & Andreas noticed that we were still requiring userspace to pass
IPC_64 in order to get the new style IPC API.

With a bit of cleanup in the kernel we can drop that requirement, and
instead only provide the new style API, which will simplify things for
userspace.

Rather than try and sneak that patch into 4.4, instead we will drop the
individual IPC calls for powerpc, and merge them again in 4.5 once the
cleanup patch has gone in.

Because we've already added sys_mlock2() as syscall #378, we don't do a
full revert of the IPC calls. Instead we drop the __NR #defines, and
send those now undefined syscall numbers to sys_ni_syscall(). This
leaves a gap in the syscall numbers, but we'll reuse them when we merge
the individual IPC calls.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Arnd Bergmann <arnd@arndb.de>