mips: remove nargs from __SYSCALL

mips: remove nargs from __SYSCALL

The __SYSCALL macro's arguments are system call number,
system call entry name and number of arguments for the
system call.

Argument- nargs in __SYSCALL(nr, entry, nargs) is neither
calculated nor used anywhere. So it would be better to
keep the implementaion as  __SYSCALL(nr, entry). This will
unifies the implementation with some other architetures
too.

Signed-off-by: Firoz Khan <firoz.khan@linaro.org>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: y2038@lists.linaro.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arch@vger.kernel.org
Cc: arnd@arndb.de
Cc: deepa.kernel@gmail.com
Cc: marcin.juszkiewicz@linaro.org