powerpc/syscalls: kill ppc32_select()

it had always been pointless - compat_sys_select() sign-extends
the first argument just fine on its own.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[mpe: Use COMPAT_SPU_NEW() to keep systbl_chk.sh happy]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>