MIPS: Compat: Zero upper 32-bit of offset_high and offset_low.

Through sys_llseek() arguably should do exactly that it doesn't which
means llseek(2) will fail for o32 processes if offset_low has bit 31 set.

As suggested by Heiko Carstens.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/linux32.c

@@ -133,9 +133,9 @@ SYSCALL_DEFINE4(32_ftruncate64, unsigned long, fd, unsigned long, __dummy,
 	return sys_ftruncate(fd, merge_64(a2, a3));
 }
 
-SYSCALL_DEFINE5(32_llseek, unsigned long, fd, unsigned long, offset_high,
-	unsigned long, offset_low, loff_t __user *, result,
-	unsigned long, origin)
+SYSCALL_DEFINE5(32_llseek, unsigned int, fd, unsigned int, offset_high,
+		unsigned int, offset_low, loff_t __user *, result,
+		unsigned int, origin)
 {
 	return sys_llseek(fd, offset_high, offset_low, result, origin);
 }