Remove getarg_klu

Remove getarg_klu

After transition from long to kernel_ulong_t we no longer need
tcp->ext_arg, and therefore a function to access it is also no longer
needed.

* defs.h (getarg_klu): Remove prototype.
* util.c (getarg_klu): Remove.
(printargs): Access tcp->u_arg directly
* bjm.c (SYS_FUNC(init_module)): Likewise.
* clone.c (SYS_FUNC(unshare)): Likewise.
* fadvise.c (SYS_FUNC(fadvise64)): Likewise.
* kcmp.c (SYS_FUNC(kcmp)): Likewise.
* kexec.c (SYS_FUNC(kexec_file_load)): Likewise.
* keyctl.c (SYS_FUNC(keyctl)): Likewise.
* lookup_dcookie.c (SYS_FUNC(lookup_dcookie)): Likewise.
* mem.c (do_mprotect): Likewise.
* mq.c (SYS_FUNC(mq_timedsend), SYS_FUNC(mq_timedreceive)): Likewise.
* pkeys.c (SYS_FUNC(pkey_alloc)): Likewise.
* prctl.c (print_prctl_args, SYS_FUNC(prctl), SYS_FUNC(arch_prctl)):
Likewise.