[MIPS] TX49x7: Fix timer register #define's

    
Fix the #define's for TX4927/37 timer reg's to match the datasheets (those
    
Signed-off-by: Konstantin Baydarov <kbaidarov@mvista.com>
Signed-off-by: Sergei Shtylyov <sshtylyov@mvista.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>