intel/compiler: also set F execution type for mixed float mode in BDW

intel/compiler: also set F execution type for mixed float mode in BDW

The section 'Execution Data Types' of 3D Media GPGPU volume, which
describes execution types, is exactly the same in BDW and SKL+.

Also, this section states that there is a single execution type, so it
makes sense that this is the wider of the two floating point types
involved in mixed float mode, which is what we do for SKL+ and CHV.

v2:
 - Make sure we also account for the destination type in mixed mode (Curro).

Acked-by: Francisco Jerez <currojerez@riseup.net>