i965/fs: Use measured Gen7 instruction timings on Gen6.

i965/fs: Use measured Gen7 instruction timings on Gen6.

x before
+ after
+------------------------------------------------------------------------------+
|   x                                   x   +                                  |
|   xx  ++                              x   +                                  |
|   xx  ++ +                           xx   ++                                 |
|x xxx x+++++          +           xxx x*x+*+++ +         x                   +|
|   |_____|____________A______A____M____M_|_______|                            |
+------------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
    x  23       8083.78       8287.83       8205.55     8162.7461     68.307951
    +  23       8107.56       8358.74       8224.33     8186.1765     71.506301
    No difference proven at 95.0% confidence

Reviewed-by: Eric Anholt <eric@anholt.net>