[MIPS] Run checksyscalls for N32 and O32 ABI

On 64-bit MIPS, only N64 ABI is checked by default.  This patch adds
some rules for other ABIs.  This results in these warnings at the
moment:

  CALL-N32 /home/git/linux-mips/scripts/checksyscalls.sh
<stdin>:148:2: warning: #warning syscall time not implemented
<stdin>:424:2: warning: #warning syscall select not implemented
<stdin>:440:2: warning: #warning syscall uselib not implemented
<stdin>:856:2: warning: #warning syscall vfork not implemented
<stdin>:868:2: warning: #warning syscall truncate64 not implemented
<stdin>:872:2: warning: #warning syscall ftruncate64 not implemented
<stdin>:876:2: warning: #warning syscall stat64 not implemented
<stdin>:880:2: warning: #warning syscall lstat64 not implemented
<stdin>:884:2: warning: #warning syscall fstat64 not implemented
<stdin>:980:2: warning: #warning syscall getdents64 not implemented
<stdin>:1176:2: warning: #warning syscall fadvise64_64 not implemented
<stdin>:1284:2: warning: #warning syscall fstatat64 not implemented
<stdin>:1364:2: warning: #warning syscall utimensat not implemented
  CALL-O32 /home/git/linux-mips/scripts/checksyscalls.sh
<stdin>:424:2: warning: #warning syscall select not implemented
<stdin>:856:2: warning: #warning syscall vfork not implemented
<stdin>:1176:2: warning: #warning syscall fadvise64_64 not implemented
<stdin>:1364:2: warning: #warning syscall utimensat not implemented
  CALL    /home/git/linux-mips/scripts/checksyscalls.sh
<stdin>:148:2: warning: #warning syscall time not implemented
<stdin>:424:2: warning: #warning syscall select not implemented
<stdin>:440:2: warning: #warning syscall uselib not implemented
<stdin>:856:2: warning: #warning syscall vfork not implemented
<stdin>:980:2: warning: #warning syscall getdents64 not implemented
<stdin>:1364:2: warning: #warning syscall utimensat not implemented

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>