alpha, ia64, mips, sh, sh64: fix the number of pipe syscall arguments

alpha, ia64, mips, sh, sh64: fix the number of pipe syscall arguments

On alpha, ia64, mips, sh, sh64, sparc, and sparc64 architectures
pipe syscall does not take arguments.

* linux/alpha/syscallent.h (pipe): Change nargs to 0.
* linux/ia64/syscallent.h (pipe): Likewise.
* linux/mips/syscallent-n32.h (pipe): Likewise.
* linux/mips/syscallent-n64.h (pipe): Likewise.
* linux/mips/syscallent-o32.h (pipe): Likewise.
* linux/sh/syscallent.h (pipe): Likewise.
* linux/sh64/syscallent.h (pipe): Likewise.