Define MAX_UDELAY_MS

    
If HZ was 1000, mdelay(2) cause overflow on multiplication in
__udelay.  We should define MAX_UDELAY_MS properly to prevent this.
    
Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>