mips: fix compat_sys_lseek syscall

This is almost compatible, but passing a negative offset should result
in a EINVAL error, but on mips o32 compat mode would seek to a large
32-bit byte offset.

Use compat_sys_lseek() to correctly sign-extend the argument.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/kernel/syscalls/syscall_o32.tbl

@@ -27,7 +27,7 @@
 17	o32	break				sys_ni_syscall
 # 18 was sys_stat
 18	o32	unused18			sys_ni_syscall
-19	o32	lseek				sys_lseek
+19	o32	lseek				sys_lseek			compat_sys_lseek
 20	o32	getpid				sys_getpid
 21	o32	mount				sys_mount
 22	o32	umount				sys_oldumount