[Nouveau] [PATCH] Do not use the default pll found in pll table v2.1 on nv50+ cards

[Eeydev]

 Hi guys,
 
Having looked at bug 30370, I believe that this is probably the best solution considering that on nv50 we set PLLs only if they exist in the pll_limits_table
 
Please review and comment. Thanks
 
--Emil