[MIPS] Fix some system calls with long long arguments

* O32 fadvise64() pass long long arguments by register pairs.  Add
  sys32 version for 64 bit kernel.
* N32 readahead() can pass a long long argument by one register.  No
  need to use sys32_readahead.

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

arch/mips/kernel/scall64-n32.S

@@ -299,7 +299,7 @@ EXPORT(sysn32_call_table)
 	PTR	sys_ni_syscall			/* res. for afs_syscall */
 	PTR	sys_ni_syscall			/* res. for security */
 	PTR	sys_gettid
-	PTR	sys32_readahead
+	PTR	sys_readahead
 	PTR	sys_setxattr			/* 6180 */
 	PTR	sys_lsetxattr
 	PTR	sys_fsetxattr